Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-12 Thread Aaron Lu 
On Mon, Mar 12, 2018 at 02:22:28PM +0100, Vlastimil Babka wrote:
> On 03/01/2018 07:28 AM, Aaron Lu wrote:
> > Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> > update pcp->count immediately after so it's natural to do it inside
> > free_pcppages_bulk().
> > 
> > No functionality or performance change is expected from this patch.
> 
> Well, it's N decrements instead of one decrement by N / assignment of
> zero. But I assume the difference is negligible anyway, right?

Yes.

> 
> > Suggested-by: Matthew Wilcox 
> > Signed-off-by: Aaron Lu 
> 
> Acked-by: Vlastimil Babka 

Thanks!

> > ---
> >  mm/page_alloc.c | 10 +++---
> >  1 file changed, 3 insertions(+), 7 deletions(-)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index cb416723538f..faa33eac1635 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> > count,
> > page = list_last_entry(list, struct page, lru);
> > /* must delete as __free_one_page list manipulates */
> > list_del(>lru);
> > +   pcp->count--;
> >  
> > mt = get_pcppage_migratetype(page);
> > /* MIGRATE_ISOLATE page should not go to pcplists */
> > @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> > per_cpu_pages *pcp)
> > local_irq_save(flags);
> > batch = READ_ONCE(pcp->batch);
> > to_drain = min(pcp->count, batch);
> > -   if (to_drain > 0) {
> > +   if (to_drain > 0)
> > free_pcppages_bulk(zone, to_drain, pcp);
> > -   pcp->count -= to_drain;
> > -   }
> > local_irq_restore(flags);
> >  }
> >  #endif
> > @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, 
> > struct zone *zone)
> > pset = per_cpu_ptr(zone->pageset, cpu);
> >  
> > pcp = >pcp;
> > -   if (pcp->count) {
> > +   if (pcp->count)
> > free_pcppages_bulk(zone, pcp->count, pcp);
> > -   pcp->count = 0;
> > -   }
> > local_irq_restore(flags);
> >  }
> >  
> > @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> > unsigned long pfn)
> > if (pcp->count >= pcp->high) {
> > unsigned long batch = READ_ONCE(pcp->batch);
> > free_pcppages_bulk(zone, batch, pcp);
> > -   pcp->count -= batch;
> > }
> >  }
> >  
> > 
>

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-12 Thread Aaron Lu 
On Mon, Mar 12, 2018 at 02:22:28PM +0100, Vlastimil Babka wrote:
> On 03/01/2018 07:28 AM, Aaron Lu wrote:
> > Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> > update pcp->count immediately after so it's natural to do it inside
> > free_pcppages_bulk().
> > 
> > No functionality or performance change is expected from this patch.
> 
> Well, it's N decrements instead of one decrement by N / assignment of
> zero. But I assume the difference is negligible anyway, right?

Yes.

> 
> > Suggested-by: Matthew Wilcox 
> > Signed-off-by: Aaron Lu 
> 
> Acked-by: Vlastimil Babka 

Thanks!

> > ---
> >  mm/page_alloc.c | 10 +++---
> >  1 file changed, 3 insertions(+), 7 deletions(-)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index cb416723538f..faa33eac1635 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> > count,
> > page = list_last_entry(list, struct page, lru);
> > /* must delete as __free_one_page list manipulates */
> > list_del(>lru);
> > +   pcp->count--;
> >  
> > mt = get_pcppage_migratetype(page);
> > /* MIGRATE_ISOLATE page should not go to pcplists */
> > @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> > per_cpu_pages *pcp)
> > local_irq_save(flags);
> > batch = READ_ONCE(pcp->batch);
> > to_drain = min(pcp->count, batch);
> > -   if (to_drain > 0) {
> > +   if (to_drain > 0)
> > free_pcppages_bulk(zone, to_drain, pcp);
> > -   pcp->count -= to_drain;
> > -   }
> > local_irq_restore(flags);
> >  }
> >  #endif
> > @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, 
> > struct zone *zone)
> > pset = per_cpu_ptr(zone->pageset, cpu);
> >  
> > pcp = >pcp;
> > -   if (pcp->count) {
> > +   if (pcp->count)
> > free_pcppages_bulk(zone, pcp->count, pcp);
> > -   pcp->count = 0;
> > -   }
> > local_irq_restore(flags);
> >  }
> >  
> > @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> > unsigned long pfn)
> > if (pcp->count >= pcp->high) {
> > unsigned long batch = READ_ONCE(pcp->batch);
> > free_pcppages_bulk(zone, batch, pcp);
> > -   pcp->count -= batch;
> > }
> >  }
> >  
> > 
>

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-12 Thread Vlastimil Babka 
On 03/01/2018 07:28 AM, Aaron Lu wrote:
> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.

Well, it's N decrements instead of one decrement by N / assignment of
zero. But I assume the difference is negligible anyway, right?

> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Acked-by: Vlastimil Babka 

> ---
>  mm/page_alloc.c | 10 +++---
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..faa33eac1635 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> count,
>   page = list_last_entry(list, struct page, lru);
>   /* must delete as __free_one_page list manipulates */
>   list_del(>lru);
> + pcp->count--;
>  
>   mt = get_pcppage_migratetype(page);
>   /* MIGRATE_ISOLATE page should not go to pcplists */
> @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> per_cpu_pages *pcp)
>   local_irq_save(flags);
>   batch = READ_ONCE(pcp->batch);
>   to_drain = min(pcp->count, batch);
> - if (to_drain > 0) {
> + if (to_drain > 0)
>   free_pcppages_bulk(zone, to_drain, pcp);
> - pcp->count -= to_drain;
> - }
>   local_irq_restore(flags);
>  }
>  #endif
> @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
> zone *zone)
>   pset = per_cpu_ptr(zone->pageset, cpu);
>  
>   pcp = >pcp;
> - if (pcp->count) {
> + if (pcp->count)
>   free_pcppages_bulk(zone, pcp->count, pcp);
> - pcp->count = 0;
> - }
>   local_irq_restore(flags);
>  }
>  
> @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> unsigned long pfn)
>   if (pcp->count >= pcp->high) {
>   unsigned long batch = READ_ONCE(pcp->batch);
>   free_pcppages_bulk(zone, batch, pcp);
> - pcp->count -= batch;
>   }
>  }
>  
>

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-12 Thread Vlastimil Babka 
On 03/01/2018 07:28 AM, Aaron Lu wrote:
> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.

Well, it's N decrements instead of one decrement by N / assignment of
zero. But I assume the difference is negligible anyway, right?

> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Acked-by: Vlastimil Babka 

> ---
>  mm/page_alloc.c | 10 +++---
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..faa33eac1635 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> count,
>   page = list_last_entry(list, struct page, lru);
>   /* must delete as __free_one_page list manipulates */
>   list_del(>lru);
> + pcp->count--;
>  
>   mt = get_pcppage_migratetype(page);
>   /* MIGRATE_ISOLATE page should not go to pcplists */
> @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> per_cpu_pages *pcp)
>   local_irq_save(flags);
>   batch = READ_ONCE(pcp->batch);
>   to_drain = min(pcp->count, batch);
> - if (to_drain > 0) {
> + if (to_drain > 0)
>   free_pcppages_bulk(zone, to_drain, pcp);
> - pcp->count -= to_drain;
> - }
>   local_irq_restore(flags);
>  }
>  #endif
> @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
> zone *zone)
>   pset = per_cpu_ptr(zone->pageset, cpu);
>  
>   pcp = >pcp;
> - if (pcp->count) {
> + if (pcp->count)
>   free_pcppages_bulk(zone, pcp->count, pcp);
> - pcp->count = 0;
> - }
>   local_irq_restore(flags);
>  }
>  
> @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> unsigned long pfn)
>   if (pcp->count >= pcp->high) {
>   unsigned long batch = READ_ONCE(pcp->batch);
>   free_pcppages_bulk(zone, batch, pcp);
> - pcp->count -= batch;
>   }
>  }
>  
>

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-01 Thread Michal Hocko 
On Thu 01-03-18 14:28:43, Aaron Lu wrote:
> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.
> 
> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Makes a lot of sense to me.
Acked-by: Michal Hocko 

> ---
>  mm/page_alloc.c | 10 +++---
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..faa33eac1635 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> count,
>   page = list_last_entry(list, struct page, lru);
>   /* must delete as __free_one_page list manipulates */
>   list_del(>lru);
> + pcp->count--;
>  
>   mt = get_pcppage_migratetype(page);
>   /* MIGRATE_ISOLATE page should not go to pcplists */
> @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> per_cpu_pages *pcp)
>   local_irq_save(flags);
>   batch = READ_ONCE(pcp->batch);
>   to_drain = min(pcp->count, batch);
> - if (to_drain > 0) {
> + if (to_drain > 0)
>   free_pcppages_bulk(zone, to_drain, pcp);
> - pcp->count -= to_drain;
> - }
>   local_irq_restore(flags);
>  }
>  #endif
> @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
> zone *zone)
>   pset = per_cpu_ptr(zone->pageset, cpu);
>  
>   pcp = >pcp;
> - if (pcp->count) {
> + if (pcp->count)
>   free_pcppages_bulk(zone, pcp->count, pcp);
> - pcp->count = 0;
> - }
>   local_irq_restore(flags);
>  }
>  
> @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> unsigned long pfn)
>   if (pcp->count >= pcp->high) {
>   unsigned long batch = READ_ONCE(pcp->batch);
>   free_pcppages_bulk(zone, batch, pcp);
> - pcp->count -= batch;
>   }
>  }
>  
> -- 
> 2.14.3
> 

-- 
Michal Hocko
SUSE Labs

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-01 Thread Michal Hocko 
On Thu 01-03-18 14:28:43, Aaron Lu wrote:
> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.
> 
> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Makes a lot of sense to me.
Acked-by: Michal Hocko 

> ---
>  mm/page_alloc.c | 10 +++---
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..faa33eac1635 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
> count,
>   page = list_last_entry(list, struct page, lru);
>   /* must delete as __free_one_page list manipulates */
>   list_del(>lru);
> + pcp->count--;
>  
>   mt = get_pcppage_migratetype(page);
>   /* MIGRATE_ISOLATE page should not go to pcplists */
> @@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
> per_cpu_pages *pcp)
>   local_irq_save(flags);
>   batch = READ_ONCE(pcp->batch);
>   to_drain = min(pcp->count, batch);
> - if (to_drain > 0) {
> + if (to_drain > 0)
>   free_pcppages_bulk(zone, to_drain, pcp);
> - pcp->count -= to_drain;
> - }
>   local_irq_restore(flags);
>  }
>  #endif
> @@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
> zone *zone)
>   pset = per_cpu_ptr(zone->pageset, cpu);
>  
>   pcp = >pcp;
> - if (pcp->count) {
> + if (pcp->count)
>   free_pcppages_bulk(zone, pcp->count, pcp);
> - pcp->count = 0;
> - }
>   local_irq_restore(flags);
>  }
>  
> @@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
> unsigned long pfn)
>   if (pcp->count >= pcp->high) {
>   unsigned long batch = READ_ONCE(pcp->batch);
>   free_pcppages_bulk(zone, batch, pcp);
> - pcp->count -= batch;
>   }
>  }
>  
> -- 
> 2.14.3
> 

-- 
Michal Hocko
SUSE Labs

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-01 Thread David Rientjes 
On Thu, 1 Mar 2018, Aaron Lu wrote:

> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.
> 
> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Acked-by: David Rientjes

Re: [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-03-01 Thread David Rientjes 
On Thu, 1 Mar 2018, Aaron Lu wrote:

> Matthew Wilcox found that all callers of free_pcppages_bulk() currently
> update pcp->count immediately after so it's natural to do it inside
> free_pcppages_bulk().
> 
> No functionality or performance change is expected from this patch.
> 
> Suggested-by: Matthew Wilcox 
> Signed-off-by: Aaron Lu 

Acked-by: David Rientjes

[PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-02-28 Thread Aaron Lu 
Matthew Wilcox found that all callers of free_pcppages_bulk() currently
update pcp->count immediately after so it's natural to do it inside
free_pcppages_bulk().

No functionality or performance change is expected from this patch.

Suggested-by: Matthew Wilcox 
Signed-off-by: Aaron Lu 
---
 mm/page_alloc.c | 10 +++---
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cb416723538f..faa33eac1635 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
count,
page = list_last_entry(list, struct page, lru);
/* must delete as __free_one_page list manipulates */
list_del(>lru);
+   pcp->count--;
 
mt = get_pcppage_migratetype(page);
/* MIGRATE_ISOLATE page should not go to pcplists */
@@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
per_cpu_pages *pcp)
local_irq_save(flags);
batch = READ_ONCE(pcp->batch);
to_drain = min(pcp->count, batch);
-   if (to_drain > 0) {
+   if (to_drain > 0)
free_pcppages_bulk(zone, to_drain, pcp);
-   pcp->count -= to_drain;
-   }
local_irq_restore(flags);
 }
 #endif
@@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
zone *zone)
pset = per_cpu_ptr(zone->pageset, cpu);
 
pcp = >pcp;
-   if (pcp->count) {
+   if (pcp->count)
free_pcppages_bulk(zone, pcp->count, pcp);
-   pcp->count = 0;
-   }
local_irq_restore(flags);
 }
 
@@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
unsigned long pfn)
if (pcp->count >= pcp->high) {
unsigned long batch = READ_ONCE(pcp->batch);
free_pcppages_bulk(zone, batch, pcp);
-   pcp->count -= batch;
}
 }
 
-- 
2.14.3

[PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside

2018-02-28 Thread Aaron Lu 
Matthew Wilcox found that all callers of free_pcppages_bulk() currently
update pcp->count immediately after so it's natural to do it inside
free_pcppages_bulk().

No functionality or performance change is expected from this patch.

Suggested-by: Matthew Wilcox 
Signed-off-by: Aaron Lu 
---
 mm/page_alloc.c | 10 +++---
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cb416723538f..faa33eac1635 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1148,6 +1148,7 @@ static void free_pcppages_bulk(struct zone *zone, int 
count,
page = list_last_entry(list, struct page, lru);
/* must delete as __free_one_page list manipulates */
list_del(>lru);
+   pcp->count--;
 
mt = get_pcppage_migratetype(page);
/* MIGRATE_ISOLATE page should not go to pcplists */
@@ -2416,10 +2417,8 @@ void drain_zone_pages(struct zone *zone, struct 
per_cpu_pages *pcp)
local_irq_save(flags);
batch = READ_ONCE(pcp->batch);
to_drain = min(pcp->count, batch);
-   if (to_drain > 0) {
+   if (to_drain > 0)
free_pcppages_bulk(zone, to_drain, pcp);
-   pcp->count -= to_drain;
-   }
local_irq_restore(flags);
 }
 #endif
@@ -2441,10 +2440,8 @@ static void drain_pages_zone(unsigned int cpu, struct 
zone *zone)
pset = per_cpu_ptr(zone->pageset, cpu);
 
pcp = >pcp;
-   if (pcp->count) {
+   if (pcp->count)
free_pcppages_bulk(zone, pcp->count, pcp);
-   pcp->count = 0;
-   }
local_irq_restore(flags);
 }
 
@@ -2668,7 +2665,6 @@ static void free_unref_page_commit(struct page *page, 
unsigned long pfn)
if (pcp->count >= pcp->high) {
unsigned long batch = READ_ONCE(pcp->batch);
free_pcppages_bulk(zone, batch, pcp);
-   pcp->count -= batch;
}
 }
 
-- 
2.14.3