Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hello, Andrew.
2012/11/20 Minchan Kim :
> Hi Joonsoo,
> Sorry for the delay.
>
> On Thu, Nov 15, 2012 at 02:09:04AM +0900, JoonSoo Kim wrote:
>> Hi, Minchan.
>>
>> 2012/11/14 Minchan Kim :
>> > On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
>> >> 2012/11/13 Minchan Kim :
>> >> > On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
>> >> >> 2012/11/3 Minchan Kim :
>> >> >> > Hi Joonsoo,
>> >> >> >
>> >> >> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
>> >> >> >> Hello, Minchan.
>> >> >> >>
>> >> >> >> 2012/11/1 Minchan Kim :
>> >> >> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
>> >> >> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
>> >> >> >> >> then re-iterate all pkmaps. It can be optimized if
>> >> >> >> >> flush_all_zero_pkmaps()
>> >> >> >> >> return index of first flushed entry. With this index,
>> >> >> >> >> we can immediately map highmem page to virtual address
>> >> >> >> >> represented by index.
>> >> >> >> >> So change return type of flush_all_zero_pkmaps()
>> >> >> >> >> and return index of first flushed entry.
>> >> >> >> >>
>> >> >> >> >> Additionally, update last_pkmap_nr to this index.
>> >> >> >> >> It is certain that entry which is below this index is occupied
>> >> >> >> >> by other mapping,
>> >> >> >> >> therefore updating last_pkmap_nr to this index is reasonable
>> >> >> >> >> optimization.
>> >> >> >> >>
>> >> >> >> >> Cc: Mel Gorman
>> >> >> >> >> Cc: Peter Zijlstra
>> >> >> >> >> Cc: Minchan Kim
>> >> >> >> >> Signed-off-by: Joonsoo Kim
>> >> >> >> >>
>> >> >> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> >> >> >> >> index ef788b5..97ad208 100644
>> >> >> >> >> --- a/include/linux/highmem.h
>> >> >> >> >> +++ b/include/linux/highmem.h
>> >> >> >> >> @@ -32,6 +32,7 @@ static inline void
>> >> >> >> >> invalidate_kernel_vmap_range(void *vaddr, int size)
>> >> >> >> >>
>> >> >> >> >> #ifdef CONFIG_HIGHMEM
>> >> >> >> >> #include
>> >> >> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>> >> >> >> >>
>> >> >> >> >> /* declarations for linux/mm/highmem.c */
>> >> >> >> >> unsigned int nr_free_highpages(void);
>> >> >> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
>> >> >> >> >> index d98b0a9..b365f7b 100644
>> >> >> >> >> --- a/mm/highmem.c
>> >> >> >> >> +++ b/mm/highmem.c
>> >> >> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
>> >> >> >> >> return virt_to_page(addr);
>> >> >> >> >> }
>> >> >> >> >>
>> >> >> >> >> -static void flush_all_zero_pkmaps(void)
>> >> >> >> >> +static unsigned int flush_all_zero_pkmaps(void)
>> >> >> >> >> {
>> >> >> >> >> int i;
>> >> >> >> >> - int need_flush = 0;
>> >> >> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
>> >> >> >> >>
>> >> >> >> >> flush_cache_kmaps();
>> >> >> >> >>
>> >> >> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
>> >> >> >> >> _page_table[i]);
>> >> >> >> >>
>> >> >> >> >> set_page_address(page, NULL);
>> >> >> >> >> - need_flush = 1;
>> >> >> >> >> + if (index == PKMAP_INVALID_INDEX)
>> >> >> >> >> + index = i;
>> >> >> >> >> }
>> >> >> >> >> - if (need_flush)
>> >> >> >> >> + if (index != PKMAP_INVALID_INDEX)
>> >> >> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
>> >> >> >> >> PKMAP_ADDR(LAST_PKMAP));
>> >> >> >> >> +
>> >> >> >> >> + return index;
>> >> >> >> >> }
>> >> >> >> >>
>> >> >> >> >> /**
>> >> >> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
>> >> >> >> >> */
>> >> >> >> >> void kmap_flush_unused(void)
>> >> >> >> >> {
>> >> >> >> >> + unsigned int index;
>> >> >> >> >> +
>> >> >> >> >> lock_kmap();
>> >> >> >> >> - flush_all_zero_pkmaps();
>> >> >> >> >> + index = flush_all_zero_pkmaps();
>> >> >> >> >> + if (index != PKMAP_INVALID_INDEX && (index <
>> >> >> >> >> last_pkmap_nr))
>> >> >> >> >> + last_pkmap_nr = index;
>> >> >> >> >
>> >> >> >> > I don't know how kmap_flush_unused is really fast path so how my
>> >> >> >> > nitpick
>> >> >> >> > is effective. Anyway,
>> >> >> >> > What problem happens if we do following as?
>> >> >> >> >
>> >> >> >> > lock()
>> >> >> >> > index = flush_all_zero_pkmaps();
>> >> >> >> > if (index != PKMAP_INVALID_INDEX)
>> >> >> >> > last_pkmap_nr = index;
>> >> >> >> > unlock();
>> >> >> >> >
>> >> >> >> > Normally, last_pkmap_nr is increased with searching empty slot in
>> >> >> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
>> >> >> >> > in kmap_flush_unused normally become either less than
>> >> >> >> > last_pkmap_nr
>> >> >> >> > or last_pkmap_nr + 1.
>> >> >> >>
>> >> >> >> There is a case that return value of kmap_flush_unused() is larger
>> >> >> >> than last_pkmap_nr.
>> >> >> >
>> >> >> > I see but why it's problem? kmap_flush_unused returns larger value
>> >> >> > than
>>
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hello, Andrew.
2012/11/20 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
Sorry for the delay.
On Thu, Nov 15, 2012 at 02:09:04AM +0900, JoonSoo Kim wrote:
Hi, Minchan.
2012/11/14 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
2012/11/13 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address
represented by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied
by other mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void
invalidate_kernel_vmap_range(void *vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index
last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my
nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than
last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value
than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped
index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot
index.
What's the benefit returning flushed flushed free slot index rather
than free slot index?
If flush_all_zero_pkmaps()
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi Joonsoo,
Sorry for the delay.
On Thu, Nov 15, 2012 at 02:09:04AM +0900, JoonSoo Kim wrote:
> Hi, Minchan.
>
> 2012/11/14 Minchan Kim :
> > On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
> >> 2012/11/13 Minchan Kim :
> >> > On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
> >> >> 2012/11/3 Minchan Kim :
> >> >> > Hi Joonsoo,
> >> >> >
> >> >> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
> >> >> >> Hello, Minchan.
> >> >> >>
> >> >> >> 2012/11/1 Minchan Kim :
> >> >> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
> >> >> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
> >> >> >> >> then re-iterate all pkmaps. It can be optimized if
> >> >> >> >> flush_all_zero_pkmaps()
> >> >> >> >> return index of first flushed entry. With this index,
> >> >> >> >> we can immediately map highmem page to virtual address
> >> >> >> >> represented by index.
> >> >> >> >> So change return type of flush_all_zero_pkmaps()
> >> >> >> >> and return index of first flushed entry.
> >> >> >> >>
> >> >> >> >> Additionally, update last_pkmap_nr to this index.
> >> >> >> >> It is certain that entry which is below this index is occupied by
> >> >> >> >> other mapping,
> >> >> >> >> therefore updating last_pkmap_nr to this index is reasonable
> >> >> >> >> optimization.
> >> >> >> >>
> >> >> >> >> Cc: Mel Gorman
> >> >> >> >> Cc: Peter Zijlstra
> >> >> >> >> Cc: Minchan Kim
> >> >> >> >> Signed-off-by: Joonsoo Kim
> >> >> >> >>
> >> >> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> >> >> >> >> index ef788b5..97ad208 100644
> >> >> >> >> --- a/include/linux/highmem.h
> >> >> >> >> +++ b/include/linux/highmem.h
> >> >> >> >> @@ -32,6 +32,7 @@ static inline void
> >> >> >> >> invalidate_kernel_vmap_range(void *vaddr, int size)
> >> >> >> >>
> >> >> >> >> #ifdef CONFIG_HIGHMEM
> >> >> >> >> #include
> >> >> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
> >> >> >> >>
> >> >> >> >> /* declarations for linux/mm/highmem.c */
> >> >> >> >> unsigned int nr_free_highpages(void);
> >> >> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
> >> >> >> >> index d98b0a9..b365f7b 100644
> >> >> >> >> --- a/mm/highmem.c
> >> >> >> >> +++ b/mm/highmem.c
> >> >> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
> >> >> >> >> return virt_to_page(addr);
> >> >> >> >> }
> >> >> >> >>
> >> >> >> >> -static void flush_all_zero_pkmaps(void)
> >> >> >> >> +static unsigned int flush_all_zero_pkmaps(void)
> >> >> >> >> {
> >> >> >> >> int i;
> >> >> >> >> - int need_flush = 0;
> >> >> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
> >> >> >> >>
> >> >> >> >> flush_cache_kmaps();
> >> >> >> >>
> >> >> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
> >> >> >> >> _page_table[i]);
> >> >> >> >>
> >> >> >> >> set_page_address(page, NULL);
> >> >> >> >> - need_flush = 1;
> >> >> >> >> + if (index == PKMAP_INVALID_INDEX)
> >> >> >> >> + index = i;
> >> >> >> >> }
> >> >> >> >> - if (need_flush)
> >> >> >> >> + if (index != PKMAP_INVALID_INDEX)
> >> >> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
> >> >> >> >> PKMAP_ADDR(LAST_PKMAP));
> >> >> >> >> +
> >> >> >> >> + return index;
> >> >> >> >> }
> >> >> >> >>
> >> >> >> >> /**
> >> >> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
> >> >> >> >> */
> >> >> >> >> void kmap_flush_unused(void)
> >> >> >> >> {
> >> >> >> >> + unsigned int index;
> >> >> >> >> +
> >> >> >> >> lock_kmap();
> >> >> >> >> - flush_all_zero_pkmaps();
> >> >> >> >> + index = flush_all_zero_pkmaps();
> >> >> >> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
> >> >> >> >> + last_pkmap_nr = index;
> >> >> >> >
> >> >> >> > I don't know how kmap_flush_unused is really fast path so how my
> >> >> >> > nitpick
> >> >> >> > is effective. Anyway,
> >> >> >> > What problem happens if we do following as?
> >> >> >> >
> >> >> >> > lock()
> >> >> >> > index = flush_all_zero_pkmaps();
> >> >> >> > if (index != PKMAP_INVALID_INDEX)
> >> >> >> > last_pkmap_nr = index;
> >> >> >> > unlock();
> >> >> >> >
> >> >> >> > Normally, last_pkmap_nr is increased with searching empty slot in
> >> >> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
> >> >> >> > in kmap_flush_unused normally become either less than last_pkmap_nr
> >> >> >> > or last_pkmap_nr + 1.
> >> >> >>
> >> >> >> There is a case that return value of kmap_flush_unused() is larger
> >> >> >> than last_pkmap_nr.
> >> >> >
> >> >> > I see but why it's problem? kmap_flush_unused returns larger value
> >> >> > than
> >> >> > last_pkmap_nr means that there is no free slot at below the value.
> >> >> > So unconditional last_pkmap_nr update is vaild.
> >> >>
> >> >> I think that this is not true.
> >> >> Look
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi Joonsoo,
Sorry for the delay.
On Thu, Nov 15, 2012 at 02:09:04AM +0900, JoonSoo Kim wrote:
Hi, Minchan.
2012/11/14 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
2012/11/13 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address
represented by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by
other mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void
invalidate_kernel_vmap_range(void *vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my
nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value
than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped
index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot
index.
What's the benefit returning flushed flushed free slot index rather than
free slot index?
If flush_all_zero_pkmaps() return free slot index rather than first
flushed free slot,
we need
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi, Minchan.
2012/11/14 Minchan Kim :
> On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
>> 2012/11/13 Minchan Kim :
>> > On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
>> >> 2012/11/3 Minchan Kim :
>> >> > Hi Joonsoo,
>> >> >
>> >> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
>> >> >> Hello, Minchan.
>> >> >>
>> >> >> 2012/11/1 Minchan Kim :
>> >> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
>> >> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
>> >> >> >> then re-iterate all pkmaps. It can be optimized if
>> >> >> >> flush_all_zero_pkmaps()
>> >> >> >> return index of first flushed entry. With this index,
>> >> >> >> we can immediately map highmem page to virtual address represented
>> >> >> >> by index.
>> >> >> >> So change return type of flush_all_zero_pkmaps()
>> >> >> >> and return index of first flushed entry.
>> >> >> >>
>> >> >> >> Additionally, update last_pkmap_nr to this index.
>> >> >> >> It is certain that entry which is below this index is occupied by
>> >> >> >> other mapping,
>> >> >> >> therefore updating last_pkmap_nr to this index is reasonable
>> >> >> >> optimization.
>> >> >> >>
>> >> >> >> Cc: Mel Gorman
>> >> >> >> Cc: Peter Zijlstra
>> >> >> >> Cc: Minchan Kim
>> >> >> >> Signed-off-by: Joonsoo Kim
>> >> >> >>
>> >> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> >> >> >> index ef788b5..97ad208 100644
>> >> >> >> --- a/include/linux/highmem.h
>> >> >> >> +++ b/include/linux/highmem.h
>> >> >> >> @@ -32,6 +32,7 @@ static inline void
>> >> >> >> invalidate_kernel_vmap_range(void *vaddr, int size)
>> >> >> >>
>> >> >> >> #ifdef CONFIG_HIGHMEM
>> >> >> >> #include
>> >> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>> >> >> >>
>> >> >> >> /* declarations for linux/mm/highmem.c */
>> >> >> >> unsigned int nr_free_highpages(void);
>> >> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
>> >> >> >> index d98b0a9..b365f7b 100644
>> >> >> >> --- a/mm/highmem.c
>> >> >> >> +++ b/mm/highmem.c
>> >> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
>> >> >> >> return virt_to_page(addr);
>> >> >> >> }
>> >> >> >>
>> >> >> >> -static void flush_all_zero_pkmaps(void)
>> >> >> >> +static unsigned int flush_all_zero_pkmaps(void)
>> >> >> >> {
>> >> >> >> int i;
>> >> >> >> - int need_flush = 0;
>> >> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
>> >> >> >>
>> >> >> >> flush_cache_kmaps();
>> >> >> >>
>> >> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
>> >> >> >> _page_table[i]);
>> >> >> >>
>> >> >> >> set_page_address(page, NULL);
>> >> >> >> - need_flush = 1;
>> >> >> >> + if (index == PKMAP_INVALID_INDEX)
>> >> >> >> + index = i;
>> >> >> >> }
>> >> >> >> - if (need_flush)
>> >> >> >> + if (index != PKMAP_INVALID_INDEX)
>> >> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
>> >> >> >> PKMAP_ADDR(LAST_PKMAP));
>> >> >> >> +
>> >> >> >> + return index;
>> >> >> >> }
>> >> >> >>
>> >> >> >> /**
>> >> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
>> >> >> >> */
>> >> >> >> void kmap_flush_unused(void)
>> >> >> >> {
>> >> >> >> + unsigned int index;
>> >> >> >> +
>> >> >> >> lock_kmap();
>> >> >> >> - flush_all_zero_pkmaps();
>> >> >> >> + index = flush_all_zero_pkmaps();
>> >> >> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
>> >> >> >> + last_pkmap_nr = index;
>> >> >> >
>> >> >> > I don't know how kmap_flush_unused is really fast path so how my
>> >> >> > nitpick
>> >> >> > is effective. Anyway,
>> >> >> > What problem happens if we do following as?
>> >> >> >
>> >> >> > lock()
>> >> >> > index = flush_all_zero_pkmaps();
>> >> >> > if (index != PKMAP_INVALID_INDEX)
>> >> >> > last_pkmap_nr = index;
>> >> >> > unlock();
>> >> >> >
>> >> >> > Normally, last_pkmap_nr is increased with searching empty slot in
>> >> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
>> >> >> > in kmap_flush_unused normally become either less than last_pkmap_nr
>> >> >> > or last_pkmap_nr + 1.
>> >> >>
>> >> >> There is a case that return value of kmap_flush_unused() is larger
>> >> >> than last_pkmap_nr.
>> >> >
>> >> > I see but why it's problem? kmap_flush_unused returns larger value than
>> >> > last_pkmap_nr means that there is no free slot at below the value.
>> >> > So unconditional last_pkmap_nr update is vaild.
>> >>
>> >> I think that this is not true.
>> >> Look at the slightly different example.
>> >>
>> >> Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
>> >> kunmapped.
>> >>
>> >> do kmap_flush_unused() => flush index 10,11 => last_pkmap = 10;
>> >> do kunmap() with index 17
>> >> do kmap_flush_unused() => flush index 17 => last_pkmap = 17?
>> >>
>> >> In this case,
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi, Minchan.
2012/11/14 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
2012/11/13 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented
by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by
other mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void
invalidate_kernel_vmap_range(void *vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my
nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot
index.
What's the benefit returning flushed flushed free slot index rather than
free slot index?
If flush_all_zero_pkmaps() return free slot index rather than first
flushed free slot,
we need another comparison like as 'if pkmap_count[i] == 0' and
need another local variable for determining whether flush is occurred or not.
I want to minimize these overhead and churning of the code, although
they are negligible.
I think
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
> 2012/11/13 Minchan Kim :
> > On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
> >> 2012/11/3 Minchan Kim :
> >> > Hi Joonsoo,
> >> >
> >> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
> >> >> Hello, Minchan.
> >> >>
> >> >> 2012/11/1 Minchan Kim :
> >> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
> >> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
> >> >> >> then re-iterate all pkmaps. It can be optimized if
> >> >> >> flush_all_zero_pkmaps()
> >> >> >> return index of first flushed entry. With this index,
> >> >> >> we can immediately map highmem page to virtual address represented
> >> >> >> by index.
> >> >> >> So change return type of flush_all_zero_pkmaps()
> >> >> >> and return index of first flushed entry.
> >> >> >>
> >> >> >> Additionally, update last_pkmap_nr to this index.
> >> >> >> It is certain that entry which is below this index is occupied by
> >> >> >> other mapping,
> >> >> >> therefore updating last_pkmap_nr to this index is reasonable
> >> >> >> optimization.
> >> >> >>
> >> >> >> Cc: Mel Gorman
> >> >> >> Cc: Peter Zijlstra
> >> >> >> Cc: Minchan Kim
> >> >> >> Signed-off-by: Joonsoo Kim
> >> >> >>
> >> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> >> >> >> index ef788b5..97ad208 100644
> >> >> >> --- a/include/linux/highmem.h
> >> >> >> +++ b/include/linux/highmem.h
> >> >> >> @@ -32,6 +32,7 @@ static inline void
> >> >> >> invalidate_kernel_vmap_range(void *vaddr, int size)
> >> >> >>
> >> >> >> #ifdef CONFIG_HIGHMEM
> >> >> >> #include
> >> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
> >> >> >>
> >> >> >> /* declarations for linux/mm/highmem.c */
> >> >> >> unsigned int nr_free_highpages(void);
> >> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
> >> >> >> index d98b0a9..b365f7b 100644
> >> >> >> --- a/mm/highmem.c
> >> >> >> +++ b/mm/highmem.c
> >> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
> >> >> >> return virt_to_page(addr);
> >> >> >> }
> >> >> >>
> >> >> >> -static void flush_all_zero_pkmaps(void)
> >> >> >> +static unsigned int flush_all_zero_pkmaps(void)
> >> >> >> {
> >> >> >> int i;
> >> >> >> - int need_flush = 0;
> >> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
> >> >> >>
> >> >> >> flush_cache_kmaps();
> >> >> >>
> >> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
> >> >> >> _page_table[i]);
> >> >> >>
> >> >> >> set_page_address(page, NULL);
> >> >> >> - need_flush = 1;
> >> >> >> + if (index == PKMAP_INVALID_INDEX)
> >> >> >> + index = i;
> >> >> >> }
> >> >> >> - if (need_flush)
> >> >> >> + if (index != PKMAP_INVALID_INDEX)
> >> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
> >> >> >> PKMAP_ADDR(LAST_PKMAP));
> >> >> >> +
> >> >> >> + return index;
> >> >> >> }
> >> >> >>
> >> >> >> /**
> >> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
> >> >> >> */
> >> >> >> void kmap_flush_unused(void)
> >> >> >> {
> >> >> >> + unsigned int index;
> >> >> >> +
> >> >> >> lock_kmap();
> >> >> >> - flush_all_zero_pkmaps();
> >> >> >> + index = flush_all_zero_pkmaps();
> >> >> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
> >> >> >> + last_pkmap_nr = index;
> >> >> >
> >> >> > I don't know how kmap_flush_unused is really fast path so how my
> >> >> > nitpick
> >> >> > is effective. Anyway,
> >> >> > What problem happens if we do following as?
> >> >> >
> >> >> > lock()
> >> >> > index = flush_all_zero_pkmaps();
> >> >> > if (index != PKMAP_INVALID_INDEX)
> >> >> > last_pkmap_nr = index;
> >> >> > unlock();
> >> >> >
> >> >> > Normally, last_pkmap_nr is increased with searching empty slot in
> >> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
> >> >> > in kmap_flush_unused normally become either less than last_pkmap_nr
> >> >> > or last_pkmap_nr + 1.
> >> >>
> >> >> There is a case that return value of kmap_flush_unused() is larger
> >> >> than last_pkmap_nr.
> >> >
> >> > I see but why it's problem? kmap_flush_unused returns larger value than
> >> > last_pkmap_nr means that there is no free slot at below the value.
> >> > So unconditional last_pkmap_nr update is vaild.
> >>
> >> I think that this is not true.
> >> Look at the slightly different example.
> >>
> >> Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
> >> kunmapped.
> >>
> >> do kmap_flush_unused() => flush index 10,11 => last_pkmap = 10;
> >> do kunmap() with index 17
> >> do kmap_flush_unused() => flush index 17 => last_pkmap = 17?
> >>
> >> In this case, unconditional last_pkmap_nr update skip one kunmapped index.
> >> So, conditional update is needed.
> >
> > Thanks for pouinting out, Joonsoo.
> > You're right. I
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
2012/11/13 Minchan Kim :
> On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
>> 2012/11/3 Minchan Kim :
>> > Hi Joonsoo,
>> >
>> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
>> >> Hello, Minchan.
>> >>
>> >> 2012/11/1 Minchan Kim :
>> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
>> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
>> >> >> then re-iterate all pkmaps. It can be optimized if
>> >> >> flush_all_zero_pkmaps()
>> >> >> return index of first flushed entry. With this index,
>> >> >> we can immediately map highmem page to virtual address represented by
>> >> >> index.
>> >> >> So change return type of flush_all_zero_pkmaps()
>> >> >> and return index of first flushed entry.
>> >> >>
>> >> >> Additionally, update last_pkmap_nr to this index.
>> >> >> It is certain that entry which is below this index is occupied by
>> >> >> other mapping,
>> >> >> therefore updating last_pkmap_nr to this index is reasonable
>> >> >> optimization.
>> >> >>
>> >> >> Cc: Mel Gorman
>> >> >> Cc: Peter Zijlstra
>> >> >> Cc: Minchan Kim
>> >> >> Signed-off-by: Joonsoo Kim
>> >> >>
>> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> >> >> index ef788b5..97ad208 100644
>> >> >> --- a/include/linux/highmem.h
>> >> >> +++ b/include/linux/highmem.h
>> >> >> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
>> >> >> *vaddr, int size)
>> >> >>
>> >> >> #ifdef CONFIG_HIGHMEM
>> >> >> #include
>> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>> >> >>
>> >> >> /* declarations for linux/mm/highmem.c */
>> >> >> unsigned int nr_free_highpages(void);
>> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
>> >> >> index d98b0a9..b365f7b 100644
>> >> >> --- a/mm/highmem.c
>> >> >> +++ b/mm/highmem.c
>> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
>> >> >> return virt_to_page(addr);
>> >> >> }
>> >> >>
>> >> >> -static void flush_all_zero_pkmaps(void)
>> >> >> +static unsigned int flush_all_zero_pkmaps(void)
>> >> >> {
>> >> >> int i;
>> >> >> - int need_flush = 0;
>> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
>> >> >>
>> >> >> flush_cache_kmaps();
>> >> >>
>> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
>> >> >> _page_table[i]);
>> >> >>
>> >> >> set_page_address(page, NULL);
>> >> >> - need_flush = 1;
>> >> >> + if (index == PKMAP_INVALID_INDEX)
>> >> >> + index = i;
>> >> >> }
>> >> >> - if (need_flush)
>> >> >> + if (index != PKMAP_INVALID_INDEX)
>> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
>> >> >> PKMAP_ADDR(LAST_PKMAP));
>> >> >> +
>> >> >> + return index;
>> >> >> }
>> >> >>
>> >> >> /**
>> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
>> >> >> */
>> >> >> void kmap_flush_unused(void)
>> >> >> {
>> >> >> + unsigned int index;
>> >> >> +
>> >> >> lock_kmap();
>> >> >> - flush_all_zero_pkmaps();
>> >> >> + index = flush_all_zero_pkmaps();
>> >> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
>> >> >> + last_pkmap_nr = index;
>> >> >
>> >> > I don't know how kmap_flush_unused is really fast path so how my nitpick
>> >> > is effective. Anyway,
>> >> > What problem happens if we do following as?
>> >> >
>> >> > lock()
>> >> > index = flush_all_zero_pkmaps();
>> >> > if (index != PKMAP_INVALID_INDEX)
>> >> > last_pkmap_nr = index;
>> >> > unlock();
>> >> >
>> >> > Normally, last_pkmap_nr is increased with searching empty slot in
>> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
>> >> > in kmap_flush_unused normally become either less than last_pkmap_nr
>> >> > or last_pkmap_nr + 1.
>> >>
>> >> There is a case that return value of kmap_flush_unused() is larger
>> >> than last_pkmap_nr.
>> >
>> > I see but why it's problem? kmap_flush_unused returns larger value than
>> > last_pkmap_nr means that there is no free slot at below the value.
>> > So unconditional last_pkmap_nr update is vaild.
>>
>> I think that this is not true.
>> Look at the slightly different example.
>>
>> Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
>>
>> do kmap_flush_unused() => flush index 10,11 => last_pkmap = 10;
>> do kunmap() with index 17
>> do kmap_flush_unused() => flush index 17 => last_pkmap = 17?
>>
>> In this case, unconditional last_pkmap_nr update skip one kunmapped index.
>> So, conditional update is needed.
>
> Thanks for pouinting out, Joonsoo.
> You're right. I misunderstood your flush_all_zero_pkmaps change.
> As your change, flush_all_zero_pkmaps returns first *flushed* free slot index.
> What's the benefit returning flushed flushed free slot index rather than free
> slot index?
If flush_all_zero_pkmaps() return free slot index rather than first
flushed free slot,
we need another comparison
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
> 2012/11/3 Minchan Kim :
> > Hi Joonsoo,
> >
> > On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
> >> Hello, Minchan.
> >>
> >> 2012/11/1 Minchan Kim :
> >> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
> >> >> In current code, after flush_all_zero_pkmaps() is invoked,
> >> >> then re-iterate all pkmaps. It can be optimized if
> >> >> flush_all_zero_pkmaps()
> >> >> return index of first flushed entry. With this index,
> >> >> we can immediately map highmem page to virtual address represented by
> >> >> index.
> >> >> So change return type of flush_all_zero_pkmaps()
> >> >> and return index of first flushed entry.
> >> >>
> >> >> Additionally, update last_pkmap_nr to this index.
> >> >> It is certain that entry which is below this index is occupied by other
> >> >> mapping,
> >> >> therefore updating last_pkmap_nr to this index is reasonable
> >> >> optimization.
> >> >>
> >> >> Cc: Mel Gorman
> >> >> Cc: Peter Zijlstra
> >> >> Cc: Minchan Kim
> >> >> Signed-off-by: Joonsoo Kim
> >> >>
> >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> >> >> index ef788b5..97ad208 100644
> >> >> --- a/include/linux/highmem.h
> >> >> +++ b/include/linux/highmem.h
> >> >> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
> >> >> *vaddr, int size)
> >> >>
> >> >> #ifdef CONFIG_HIGHMEM
> >> >> #include
> >> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
> >> >>
> >> >> /* declarations for linux/mm/highmem.c */
> >> >> unsigned int nr_free_highpages(void);
> >> >> diff --git a/mm/highmem.c b/mm/highmem.c
> >> >> index d98b0a9..b365f7b 100644
> >> >> --- a/mm/highmem.c
> >> >> +++ b/mm/highmem.c
> >> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
> >> >> return virt_to_page(addr);
> >> >> }
> >> >>
> >> >> -static void flush_all_zero_pkmaps(void)
> >> >> +static unsigned int flush_all_zero_pkmaps(void)
> >> >> {
> >> >> int i;
> >> >> - int need_flush = 0;
> >> >> + unsigned int index = PKMAP_INVALID_INDEX;
> >> >>
> >> >> flush_cache_kmaps();
> >> >>
> >> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
> >> >> _page_table[i]);
> >> >>
> >> >> set_page_address(page, NULL);
> >> >> - need_flush = 1;
> >> >> + if (index == PKMAP_INVALID_INDEX)
> >> >> + index = i;
> >> >> }
> >> >> - if (need_flush)
> >> >> + if (index != PKMAP_INVALID_INDEX)
> >> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
> >> >> PKMAP_ADDR(LAST_PKMAP));
> >> >> +
> >> >> + return index;
> >> >> }
> >> >>
> >> >> /**
> >> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
> >> >> */
> >> >> void kmap_flush_unused(void)
> >> >> {
> >> >> + unsigned int index;
> >> >> +
> >> >> lock_kmap();
> >> >> - flush_all_zero_pkmaps();
> >> >> + index = flush_all_zero_pkmaps();
> >> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
> >> >> + last_pkmap_nr = index;
> >> >
> >> > I don't know how kmap_flush_unused is really fast path so how my nitpick
> >> > is effective. Anyway,
> >> > What problem happens if we do following as?
> >> >
> >> > lock()
> >> > index = flush_all_zero_pkmaps();
> >> > if (index != PKMAP_INVALID_INDEX)
> >> > last_pkmap_nr = index;
> >> > unlock();
> >> >
> >> > Normally, last_pkmap_nr is increased with searching empty slot in
> >> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
> >> > in kmap_flush_unused normally become either less than last_pkmap_nr
> >> > or last_pkmap_nr + 1.
> >>
> >> There is a case that return value of kmap_flush_unused() is larger
> >> than last_pkmap_nr.
> >
> > I see but why it's problem? kmap_flush_unused returns larger value than
> > last_pkmap_nr means that there is no free slot at below the value.
> > So unconditional last_pkmap_nr update is vaild.
>
> I think that this is not true.
> Look at the slightly different example.
>
> Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
>
> do kmap_flush_unused() => flush index 10,11 => last_pkmap = 10;
> do kunmap() with index 17
> do kmap_flush_unused() => flush index 17 => last_pkmap = 17?
>
> In this case, unconditional last_pkmap_nr update skip one kunmapped index.
> So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot index.
What's the benefit returning flushed flushed free slot index rather than free
slot index?
I think flush_all_zero_pkmaps should return first free slot because customer of
flush_all_zero_pkmaps doesn't care whether it's just flushed or not.
What he want is just free or not. In such case, we can remove above check and
it makes
flusha_all_zero_pkmaps more
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by
index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by other
mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot index.
What's the benefit returning flushed flushed free slot index rather than free
slot index?
I think flush_all_zero_pkmaps should return first free slot because customer of
flush_all_zero_pkmaps doesn't care whether it's just flushed or not.
What he want is just free or not. In such case, we can remove above check and
it makes
flusha_all_zero_pkmaps more intuitive.
--
Kind Regards,
Minchan Kim
--
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
2012/11/13 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by
index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by
other mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot index.
What's the benefit returning flushed flushed free slot index rather than free
slot index?
If flush_all_zero_pkmaps() return free slot index rather than first
flushed free slot,
we need another comparison like as 'if pkmap_count[i] == 0' and
need another local variable for determining whether flush is occurred or not.
I want to minimize these overhead and churning of the code, although
they are negligible.
I think flush_all_zero_pkmaps should return first free slot because customer
of
flush_all_zero_pkmaps doesn't care whether it's just flushed or not.
What he want is just free or not. In such case, we can remove above check and
it makes
flusha_all_zero_pkmaps more intuitive.
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Tue, Nov 13, 2012 at 11:12:28PM +0900, JoonSoo Kim wrote:
2012/11/13 Minchan Kim minc...@kernel.org:
On Tue, Nov 13, 2012 at 09:30:57AM +0900, JoonSoo Kim wrote:
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if
flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented
by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by
other mapping,
therefore updating last_pkmap_nr to this index is reasonable
optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void
invalidate_kernel_vmap_range(void *vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my
nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is
kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
Thanks for pouinting out, Joonsoo.
You're right. I misunderstood your flush_all_zero_pkmaps change.
As your change, flush_all_zero_pkmaps returns first *flushed* free slot
index.
What's the benefit returning flushed flushed free slot index rather than
free slot index?
If flush_all_zero_pkmaps() return free slot index rather than first
flushed free slot,
we need another comparison like as 'if pkmap_count[i] == 0' and
need another local variable for determining whether flush is occurred or not.
I want to minimize these overhead and churning of the code, although
they are negligible.
I think flush_all_zero_pkmaps should return first free slot because
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
2012/11/3 Minchan Kim :
> Hi Joonsoo,
>
> On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
>> Hello, Minchan.
>>
>> 2012/11/1 Minchan Kim :
>> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
>> >> In current code, after flush_all_zero_pkmaps() is invoked,
>> >> then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
>> >> return index of first flushed entry. With this index,
>> >> we can immediately map highmem page to virtual address represented by
>> >> index.
>> >> So change return type of flush_all_zero_pkmaps()
>> >> and return index of first flushed entry.
>> >>
>> >> Additionally, update last_pkmap_nr to this index.
>> >> It is certain that entry which is below this index is occupied by other
>> >> mapping,
>> >> therefore updating last_pkmap_nr to this index is reasonable optimization.
>> >>
>> >> Cc: Mel Gorman
>> >> Cc: Peter Zijlstra
>> >> Cc: Minchan Kim
>> >> Signed-off-by: Joonsoo Kim
>> >>
>> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> >> index ef788b5..97ad208 100644
>> >> --- a/include/linux/highmem.h
>> >> +++ b/include/linux/highmem.h
>> >> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
>> >> *vaddr, int size)
>> >>
>> >> #ifdef CONFIG_HIGHMEM
>> >> #include
>> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>> >>
>> >> /* declarations for linux/mm/highmem.c */
>> >> unsigned int nr_free_highpages(void);
>> >> diff --git a/mm/highmem.c b/mm/highmem.c
>> >> index d98b0a9..b365f7b 100644
>> >> --- a/mm/highmem.c
>> >> +++ b/mm/highmem.c
>> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
>> >> return virt_to_page(addr);
>> >> }
>> >>
>> >> -static void flush_all_zero_pkmaps(void)
>> >> +static unsigned int flush_all_zero_pkmaps(void)
>> >> {
>> >> int i;
>> >> - int need_flush = 0;
>> >> + unsigned int index = PKMAP_INVALID_INDEX;
>> >>
>> >> flush_cache_kmaps();
>> >>
>> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
>> >> _page_table[i]);
>> >>
>> >> set_page_address(page, NULL);
>> >> - need_flush = 1;
>> >> + if (index == PKMAP_INVALID_INDEX)
>> >> + index = i;
>> >> }
>> >> - if (need_flush)
>> >> + if (index != PKMAP_INVALID_INDEX)
>> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
>> >> PKMAP_ADDR(LAST_PKMAP));
>> >> +
>> >> + return index;
>> >> }
>> >>
>> >> /**
>> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
>> >> */
>> >> void kmap_flush_unused(void)
>> >> {
>> >> + unsigned int index;
>> >> +
>> >> lock_kmap();
>> >> - flush_all_zero_pkmaps();
>> >> + index = flush_all_zero_pkmaps();
>> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
>> >> + last_pkmap_nr = index;
>> >
>> > I don't know how kmap_flush_unused is really fast path so how my nitpick
>> > is effective. Anyway,
>> > What problem happens if we do following as?
>> >
>> > lock()
>> > index = flush_all_zero_pkmaps();
>> > if (index != PKMAP_INVALID_INDEX)
>> > last_pkmap_nr = index;
>> > unlock();
>> >
>> > Normally, last_pkmap_nr is increased with searching empty slot in
>> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
>> > in kmap_flush_unused normally become either less than last_pkmap_nr
>> > or last_pkmap_nr + 1.
>>
>> There is a case that return value of kmap_flush_unused() is larger
>> than last_pkmap_nr.
>
> I see but why it's problem? kmap_flush_unused returns larger value than
> last_pkmap_nr means that there is no free slot at below the value.
> So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
do kmap_flush_unused() => flush index 10,11 => last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() => flush index 17 => last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
>> Look at the following example.
>>
>> Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
>>
>> do kmap_flush_unused() => flush index 10 => last_pkmap = 10;
>> do kunmap() with index 17
>> do kmap_flush_unused() => flush index 17
>>
>> So, little dirty implementation is needed.
>>
>> Thanks.
>
> --
> Kind Regards,
> Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
2012/11/3 Minchan Kim minc...@kernel.org:
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by
index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by other
mapping,
therefore updating last_pkmap_nr to this index is reasonable optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
I think that this is not true.
Look at the slightly different example.
Assume last_pkmap = 20 and index 1-9, 12-19 is kmapped. 10, 11 is kunmapped.
do kmap_flush_unused() = flush index 10,11 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17 = last_pkmap = 17?
In this case, unconditional last_pkmap_nr update skip one kunmapped index.
So, conditional update is needed.
Look at the following example.
Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
do kmap_flush_unused() = flush index 10 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17
So, little dirty implementation is needed.
Thanks.
--
Kind Regards,
Minchan Kim
--
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Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
> Hello, Minchan.
>
> 2012/11/1 Minchan Kim :
> > On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
> >> In current code, after flush_all_zero_pkmaps() is invoked,
> >> then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
> >> return index of first flushed entry. With this index,
> >> we can immediately map highmem page to virtual address represented by
> >> index.
> >> So change return type of flush_all_zero_pkmaps()
> >> and return index of first flushed entry.
> >>
> >> Additionally, update last_pkmap_nr to this index.
> >> It is certain that entry which is below this index is occupied by other
> >> mapping,
> >> therefore updating last_pkmap_nr to this index is reasonable optimization.
> >>
> >> Cc: Mel Gorman
> >> Cc: Peter Zijlstra
> >> Cc: Minchan Kim
> >> Signed-off-by: Joonsoo Kim
> >>
> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> >> index ef788b5..97ad208 100644
> >> --- a/include/linux/highmem.h
> >> +++ b/include/linux/highmem.h
> >> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
> >> *vaddr, int size)
> >>
> >> #ifdef CONFIG_HIGHMEM
> >> #include
> >> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
> >>
> >> /* declarations for linux/mm/highmem.c */
> >> unsigned int nr_free_highpages(void);
> >> diff --git a/mm/highmem.c b/mm/highmem.c
> >> index d98b0a9..b365f7b 100644
> >> --- a/mm/highmem.c
> >> +++ b/mm/highmem.c
> >> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
> >> return virt_to_page(addr);
> >> }
> >>
> >> -static void flush_all_zero_pkmaps(void)
> >> +static unsigned int flush_all_zero_pkmaps(void)
> >> {
> >> int i;
> >> - int need_flush = 0;
> >> + unsigned int index = PKMAP_INVALID_INDEX;
> >>
> >> flush_cache_kmaps();
> >>
> >> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
> >> _page_table[i]);
> >>
> >> set_page_address(page, NULL);
> >> - need_flush = 1;
> >> + if (index == PKMAP_INVALID_INDEX)
> >> + index = i;
> >> }
> >> - if (need_flush)
> >> + if (index != PKMAP_INVALID_INDEX)
> >> flush_tlb_kernel_range(PKMAP_ADDR(0),
> >> PKMAP_ADDR(LAST_PKMAP));
> >> +
> >> + return index;
> >> }
> >>
> >> /**
> >> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
> >> */
> >> void kmap_flush_unused(void)
> >> {
> >> + unsigned int index;
> >> +
> >> lock_kmap();
> >> - flush_all_zero_pkmaps();
> >> + index = flush_all_zero_pkmaps();
> >> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
> >> + last_pkmap_nr = index;
> >
> > I don't know how kmap_flush_unused is really fast path so how my nitpick
> > is effective. Anyway,
> > What problem happens if we do following as?
> >
> > lock()
> > index = flush_all_zero_pkmaps();
> > if (index != PKMAP_INVALID_INDEX)
> > last_pkmap_nr = index;
> > unlock();
> >
> > Normally, last_pkmap_nr is increased with searching empty slot in
> > map_new_virtual. So I expect return value of flush_all_zero_pkmaps
> > in kmap_flush_unused normally become either less than last_pkmap_nr
> > or last_pkmap_nr + 1.
>
> There is a case that return value of kmap_flush_unused() is larger
> than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
> Look at the following example.
>
> Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
>
> do kmap_flush_unused() => flush index 10 => last_pkmap = 10;
> do kunmap() with index 17
> do kmap_flush_unused() => flush index 17
>
> So, little dirty implementation is needed.
>
> Thanks.
--
Kind Regards,
Minchan Kim
--
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Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hello, Minchan.
2012/11/1 Minchan Kim :
> On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
>> In current code, after flush_all_zero_pkmaps() is invoked,
>> then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
>> return index of first flushed entry. With this index,
>> we can immediately map highmem page to virtual address represented by index.
>> So change return type of flush_all_zero_pkmaps()
>> and return index of first flushed entry.
>>
>> Additionally, update last_pkmap_nr to this index.
>> It is certain that entry which is below this index is occupied by other
>> mapping,
>> therefore updating last_pkmap_nr to this index is reasonable optimization.
>>
>> Cc: Mel Gorman
>> Cc: Peter Zijlstra
>> Cc: Minchan Kim
>> Signed-off-by: Joonsoo Kim
>>
>> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> index ef788b5..97ad208 100644
>> --- a/include/linux/highmem.h
>> +++ b/include/linux/highmem.h
>> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
>> *vaddr, int size)
>>
>> #ifdef CONFIG_HIGHMEM
>> #include
>> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>>
>> /* declarations for linux/mm/highmem.c */
>> unsigned int nr_free_highpages(void);
>> diff --git a/mm/highmem.c b/mm/highmem.c
>> index d98b0a9..b365f7b 100644
>> --- a/mm/highmem.c
>> +++ b/mm/highmem.c
>> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
>> return virt_to_page(addr);
>> }
>>
>> -static void flush_all_zero_pkmaps(void)
>> +static unsigned int flush_all_zero_pkmaps(void)
>> {
>> int i;
>> - int need_flush = 0;
>> + unsigned int index = PKMAP_INVALID_INDEX;
>>
>> flush_cache_kmaps();
>>
>> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
>> _page_table[i]);
>>
>> set_page_address(page, NULL);
>> - need_flush = 1;
>> + if (index == PKMAP_INVALID_INDEX)
>> + index = i;
>> }
>> - if (need_flush)
>> + if (index != PKMAP_INVALID_INDEX)
>> flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
>> +
>> + return index;
>> }
>>
>> /**
>> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
>> */
>> void kmap_flush_unused(void)
>> {
>> + unsigned int index;
>> +
>> lock_kmap();
>> - flush_all_zero_pkmaps();
>> + index = flush_all_zero_pkmaps();
>> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
>> + last_pkmap_nr = index;
>
> I don't know how kmap_flush_unused is really fast path so how my nitpick
> is effective. Anyway,
> What problem happens if we do following as?
>
> lock()
> index = flush_all_zero_pkmaps();
> if (index != PKMAP_INVALID_INDEX)
> last_pkmap_nr = index;
> unlock();
>
> Normally, last_pkmap_nr is increased with searching empty slot in
> map_new_virtual. So I expect return value of flush_all_zero_pkmaps
> in kmap_flush_unused normally become either less than last_pkmap_nr
> or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
Look at the following example.
Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
do kmap_flush_unused() => flush index 10 => last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() => flush index 17
So, little dirty implementation is needed.
Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by other
mapping,
therefore updating last_pkmap_nr to this index is reasonable optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
Look at the following example.
Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
do kmap_flush_unused() = flush index 10 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17
So, little dirty implementation is needed.
Thanks.
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
Hi Joonsoo,
On Sat, Nov 03, 2012 at 04:07:25AM +0900, JoonSoo Kim wrote:
Hello, Minchan.
2012/11/1 Minchan Kim minc...@kernel.org:
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by
index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by other
mapping,
therefore updating last_pkmap_nr to this index is reasonable optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0),
PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
There is a case that return value of kmap_flush_unused() is larger
than last_pkmap_nr.
I see but why it's problem? kmap_flush_unused returns larger value than
last_pkmap_nr means that there is no free slot at below the value.
So unconditional last_pkmap_nr update is vaild.
Look at the following example.
Assume last_pkmap = 20 and index 1-9, 11-19 is kmapped. 10 is kunmapped.
do kmap_flush_unused() = flush index 10 = last_pkmap = 10;
do kunmap() with index 17
do kmap_flush_unused() = flush index 17
So, little dirty implementation is needed.
Thanks.
--
Kind Regards,
Minchan Kim
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
> In current code, after flush_all_zero_pkmaps() is invoked,
> then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
> return index of first flushed entry. With this index,
> we can immediately map highmem page to virtual address represented by index.
> So change return type of flush_all_zero_pkmaps()
> and return index of first flushed entry.
>
> Additionally, update last_pkmap_nr to this index.
> It is certain that entry which is below this index is occupied by other
> mapping,
> therefore updating last_pkmap_nr to this index is reasonable optimization.
>
> Cc: Mel Gorman
> Cc: Peter Zijlstra
> Cc: Minchan Kim
> Signed-off-by: Joonsoo Kim
>
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index ef788b5..97ad208 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
> *vaddr, int size)
>
> #ifdef CONFIG_HIGHMEM
> #include
> +#define PKMAP_INVALID_INDEX (LAST_PKMAP)
>
> /* declarations for linux/mm/highmem.c */
> unsigned int nr_free_highpages(void);
> diff --git a/mm/highmem.c b/mm/highmem.c
> index d98b0a9..b365f7b 100644
> --- a/mm/highmem.c
> +++ b/mm/highmem.c
> @@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
> return virt_to_page(addr);
> }
>
> -static void flush_all_zero_pkmaps(void)
> +static unsigned int flush_all_zero_pkmaps(void)
> {
> int i;
> - int need_flush = 0;
> + unsigned int index = PKMAP_INVALID_INDEX;
>
> flush_cache_kmaps();
>
> @@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
> _page_table[i]);
>
> set_page_address(page, NULL);
> - need_flush = 1;
> + if (index == PKMAP_INVALID_INDEX)
> + index = i;
> }
> - if (need_flush)
> + if (index != PKMAP_INVALID_INDEX)
> flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
> +
> + return index;
> }
>
> /**
> @@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
> */
> void kmap_flush_unused(void)
> {
> + unsigned int index;
> +
> lock_kmap();
> - flush_all_zero_pkmaps();
> + index = flush_all_zero_pkmaps();
> + if (index != PKMAP_INVALID_INDEX && (index < last_pkmap_nr))
> + last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
> unlock_kmap();
> }
>
> static inline unsigned long map_new_virtual(struct page *page)
> {
> unsigned long vaddr;
> + unsigned int index = PKMAP_INVALID_INDEX;
> int count;
>
> start:
> @@ -168,40 +176,45 @@ start:
> for (;;) {
> last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
> if (!last_pkmap_nr) {
> - flush_all_zero_pkmaps();
> - count = LAST_PKMAP;
> + index = flush_all_zero_pkmaps();
> + break;
> }
> - if (!pkmap_count[last_pkmap_nr])
> + if (!pkmap_count[last_pkmap_nr]) {
> + index = last_pkmap_nr;
> break; /* Found a usable entry */
> - if (--count)
> - continue;
> -
> - /*
> - * Sleep for somebody else to unmap their entries
> - */
> - {
> - DECLARE_WAITQUEUE(wait, current);
> -
> - __set_current_state(TASK_UNINTERRUPTIBLE);
> - add_wait_queue(_map_wait, );
> - unlock_kmap();
> - schedule();
> - remove_wait_queue(_map_wait, );
> - lock_kmap();
> -
> - /* Somebody else might have mapped it while we slept */
> - if (page_address(page))
> - return (unsigned long)page_address(page);
> -
> - /* Re-start */
> - goto start;
> }
> + if (--count == 0)
> + break;
> }
> - vaddr = PKMAP_ADDR(last_pkmap_nr);
> +
> + /*
> + * Sleep for somebody else to unmap their entries
> + */
> + if (index == PKMAP_INVALID_INDEX) {
> + DECLARE_WAITQUEUE(wait, current);
> +
> + __set_current_state(TASK_UNINTERRUPTIBLE);
> + add_wait_queue(_map_wait, );
> + unlock_kmap();
> +
Re: [PATCH v2 4/5] mm, highmem: makes flush_all_zero_pkmaps() return index of first flushed entry
On Thu, Nov 01, 2012 at 01:56:36AM +0900, Joonsoo Kim wrote:
In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
return index of first flushed entry. With this index,
we can immediately map highmem page to virtual address represented by index.
So change return type of flush_all_zero_pkmaps()
and return index of first flushed entry.
Additionally, update last_pkmap_nr to this index.
It is certain that entry which is below this index is occupied by other
mapping,
therefore updating last_pkmap_nr to this index is reasonable optimization.
Cc: Mel Gorman m...@csn.ul.ie
Cc: Peter Zijlstra a.p.zijls...@chello.nl
Cc: Minchan Kim minc...@kernel.org
Signed-off-by: Joonsoo Kim js1...@gmail.com
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..97ad208 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void
*vaddr, int size)
#ifdef CONFIG_HIGHMEM
#include asm/highmem.h
+#define PKMAP_INVALID_INDEX (LAST_PKMAP)
/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
diff --git a/mm/highmem.c b/mm/highmem.c
index d98b0a9..b365f7b 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
return virt_to_page(addr);
}
-static void flush_all_zero_pkmaps(void)
+static unsigned int flush_all_zero_pkmaps(void)
{
int i;
- int need_flush = 0;
+ unsigned int index = PKMAP_INVALID_INDEX;
flush_cache_kmaps();
@@ -141,10 +141,13 @@ static void flush_all_zero_pkmaps(void)
pkmap_page_table[i]);
set_page_address(page, NULL);
- need_flush = 1;
+ if (index == PKMAP_INVALID_INDEX)
+ index = i;
}
- if (need_flush)
+ if (index != PKMAP_INVALID_INDEX)
flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
+
+ return index;
}
/**
@@ -152,14 +155,19 @@ static void flush_all_zero_pkmaps(void)
*/
void kmap_flush_unused(void)
{
+ unsigned int index;
+
lock_kmap();
- flush_all_zero_pkmaps();
+ index = flush_all_zero_pkmaps();
+ if (index != PKMAP_INVALID_INDEX (index last_pkmap_nr))
+ last_pkmap_nr = index;
I don't know how kmap_flush_unused is really fast path so how my nitpick
is effective. Anyway,
What problem happens if we do following as?
lock()
index = flush_all_zero_pkmaps();
if (index != PKMAP_INVALID_INDEX)
last_pkmap_nr = index;
unlock();
Normally, last_pkmap_nr is increased with searching empty slot in
map_new_virtual. So I expect return value of flush_all_zero_pkmaps
in kmap_flush_unused normally become either less than last_pkmap_nr
or last_pkmap_nr + 1.
unlock_kmap();
}
static inline unsigned long map_new_virtual(struct page *page)
{
unsigned long vaddr;
+ unsigned int index = PKMAP_INVALID_INDEX;
int count;
start:
@@ -168,40 +176,45 @@ start:
for (;;) {
last_pkmap_nr = (last_pkmap_nr + 1) LAST_PKMAP_MASK;
if (!last_pkmap_nr) {
- flush_all_zero_pkmaps();
- count = LAST_PKMAP;
+ index = flush_all_zero_pkmaps();
+ break;
}
- if (!pkmap_count[last_pkmap_nr])
+ if (!pkmap_count[last_pkmap_nr]) {
+ index = last_pkmap_nr;
break; /* Found a usable entry */
- if (--count)
- continue;
-
- /*
- * Sleep for somebody else to unmap their entries
- */
- {
- DECLARE_WAITQUEUE(wait, current);
-
- __set_current_state(TASK_UNINTERRUPTIBLE);
- add_wait_queue(pkmap_map_wait, wait);
- unlock_kmap();
- schedule();
- remove_wait_queue(pkmap_map_wait, wait);
- lock_kmap();
-
- /* Somebody else might have mapped it while we slept */
- if (page_address(page))
- return (unsigned long)page_address(page);
-
- /* Re-start */
- goto start;
}
+ if (--count == 0)
+ break;
}
- vaddr = PKMAP_ADDR(last_pkmap_nr);
+
+ /*
+ * Sleep for somebody else to unmap their entries
+ */
+ if (index == PKMAP_INVALID_INDEX) {
+ DECLARE_WAITQUEUE(wait, current);
+
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ add_wait_queue(pkmap_map_wait, wait);
+ unlock_kmap();
+ schedule();
+
