Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Tue, Aug 25, 2015 at 01:09:35PM +0200, Vlastimil Babka wrote:
> On 08/25/2015 12:33 PM, Mel Gorman wrote:
> >On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
> >>On 24.8.2015 15:16, Mel Gorman wrote:
> >
> > return read_seqcount_retry(>mems_allowed_seq, seq);
> >@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t
> >nodemask)
> >
> > #else /* !CONFIG_CPUSETS */
> >
> >-static inline bool cpusets_enabled(void) { return false; }
> >+static inline bool cpusets_mems_enabled(void) { return false; }
> >
> > static inline int cpuset_init(void) { return 0; }
> > static inline void cpuset_init_smp(void) {}
> >diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> >index 62ae28d8ae8d..2c1c3bf54d15 100644
> >--- a/mm/page_alloc.c
> >+++ b/mm/page_alloc.c
> >@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned
> >int order, int alloc_flags,
> > if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
> > !zlc_zone_worth_trying(zonelist, z,
> > allowednodes))
> > continue;
> >-if (cpusets_enabled() &&
> >+if (cpusets_mems_enabled() &&
> > (alloc_flags & ALLOC_CPUSET) &&
> > !cpuset_zone_allowed(zone, gfp_mask))
> > continue;
>
> Here the benefits are less clear. I guess cpuset_zone_allowed() is
> potentially costly...
>
> Heck, shouldn't we just start the static key on -1 (if possible), so that
> it's enabled only when there's 2+ cpusets?
> >>
> >>Hm wait a minute, that's what already happens:
> >>
> >>static inline int nr_cpusets(void)
> >>{
> >> /* jump label reference count + the top-level cpuset */
> >> return static_key_count(_enabled_key) + 1;
> >>}
> >>
> >>I.e. if there's only the root cpuset, static key is disabled, so I think
> >>this
> >>patch is moot after all?
> >>
> >
> >static_key_count is an atomic read on a field in struct static_key where
> >as static_key_false is a arch_static_branch which can be eliminated. The
> >patch eliminates an atomic read so I didn't think it was moot.
>
> Sorry I wasn't clear enough. My point is that AFAICS cpusets_enabled() will
> only return true if there are more cpusets than the root (top-level) one.
> So the current cpusets_enabled() checks should be enough. Checking that
> "nr_cpusets() > 1" only duplicates what is already covered by
> cpusets_enabled() - see the nr_cpusets() listing above. I.e. David's premise
> was wrong.
>
/me slaps self
I should have spotted that. Thanks.
--
Mel Gorman
SUSE Labs
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon 24-08-15 13:09:43, Mel Gorman wrote:
> David Rientjes correctly pointed out that the "root cpuset may not exclude
> mems on the system so, even if mounted, there's no need to check or be
> worried about concurrent change when there is only one cpuset".
Hmm, but cpuset_inc() is called only from cpuset_css_online and only
when it is called with non-NULL css->parent AFAICS. This means that the
static key should be still false after the root cpuset is created.
> The three checks for cpusets_enabled() care whether a cpuset exists that
> can limit memory, not that cpuset is enabled as such. This patch replaces
> cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
> cpuset exists that can limit memory and updates the appropriate call sites.
>
> Signed-off-by: Mel Gorman
> ---
> include/linux/cpuset.h | 16 +---
> mm/page_alloc.c| 2 +-
> 2 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> index 6eb27cb480b7..1e823870987e 100644
> --- a/include/linux/cpuset.h
> +++ b/include/linux/cpuset.h
> @@ -17,10 +17,6 @@
> #ifdef CONFIG_CPUSETS
>
> extern struct static_key cpusets_enabled_key;
> -static inline bool cpusets_enabled(void)
> -{
> - return static_key_false(_enabled_key);
> -}
>
> static inline int nr_cpusets(void)
> {
> @@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
> return static_key_count(_enabled_key) + 1;
> }
>
> +/* Returns true if a cpuset exists that can set cpuset.mems */
> +static inline bool cpusets_mems_enabled(void)
> +{
> + return nr_cpusets() > 1;
> +}
> +
> static inline void cpuset_inc(void)
> {
> static_key_slow_inc(_enabled_key);
> @@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
> task_struct *p);
> */
> static inline unsigned int read_mems_allowed_begin(void)
> {
> - if (!cpusets_enabled())
> + if (!cpusets_mems_enabled())
> return 0;
>
> return read_seqcount_begin(>mems_allowed_seq);
> @@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
> */
> static inline bool read_mems_allowed_retry(unsigned int seq)
> {
> - if (!cpusets_enabled())
> + if (!cpusets_mems_enabled())
> return false;
>
> return read_seqcount_retry(>mems_allowed_seq, seq);
> @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
>
> #else /* !CONFIG_CPUSETS */
>
> -static inline bool cpusets_enabled(void) { return false; }
> +static inline bool cpusets_mems_enabled(void) { return false; }
>
> static inline int cpuset_init(void) { return 0; }
> static inline void cpuset_init_smp(void) {}
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 62ae28d8ae8d..2c1c3bf54d15 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
> order, int alloc_flags,
> if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
> !zlc_zone_worth_trying(zonelist, z, allowednodes))
> continue;
> - if (cpusets_enabled() &&
> + if (cpusets_mems_enabled() &&
> (alloc_flags & ALLOC_CPUSET) &&
> !cpuset_zone_allowed(zone, gfp_mask))
> continue;
> --
> 2.4.6
--
Michal Hocko
SUSE Labs
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon 24-08-15 13:09:43, Mel Gorman wrote:
David Rientjes correctly pointed out that the root cpuset may not exclude
mems on the system so, even if mounted, there's no need to check or be
worried about concurrent change when there is only one cpuset.
Hmm, but cpuset_inc() is called only from cpuset_css_online and only
when it is called with non-NULL css-parent AFAICS. This means that the
static key should be still false after the root cpuset is created.
The three checks for cpusets_enabled() care whether a cpuset exists that
can limit memory, not that cpuset is enabled as such. This patch replaces
cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
cpuset exists that can limit memory and updates the appropriate call sites.
Signed-off-by: Mel Gorman mgor...@suse.de
---
include/linux/cpuset.h | 16 +---
mm/page_alloc.c| 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 6eb27cb480b7..1e823870987e 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,10 +17,6 @@
#ifdef CONFIG_CPUSETS
extern struct static_key cpusets_enabled_key;
-static inline bool cpusets_enabled(void)
-{
- return static_key_false(cpusets_enabled_key);
-}
static inline int nr_cpusets(void)
{
@@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
return static_key_count(cpusets_enabled_key) + 1;
}
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+ return nr_cpusets() 1;
+}
+
static inline void cpuset_inc(void)
{
static_key_slow_inc(cpusets_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(current-mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return false;
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
--
2.4.6
--
Michal Hocko
SUSE Labs
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Tue, Aug 25, 2015 at 01:09:35PM +0200, Vlastimil Babka wrote:
On 08/25/2015 12:33 PM, Mel Gorman wrote:
On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
On 24.8.2015 15:16, Mel Gorman wrote:
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t
nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned
int order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z,
allowednodes))
continue;
-if (cpusets_enabled()
+if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(cpusets_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think
this
patch is moot after all?
static_key_count is an atomic read on a field in struct static_key where
as static_key_false is a arch_static_branch which can be eliminated. The
patch eliminates an atomic read so I didn't think it was moot.
Sorry I wasn't clear enough. My point is that AFAICS cpusets_enabled() will
only return true if there are more cpusets than the root (top-level) one.
So the current cpusets_enabled() checks should be enough. Checking that
nr_cpusets() 1 only duplicates what is already covered by
cpusets_enabled() - see the nr_cpusets() listing above. I.e. David's premise
was wrong.
/me slaps self
I should have spotted that. Thanks.
--
Mel Gorman
SUSE Labs
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 08/25/2015 12:33 PM, Mel Gorman wrote:
On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
On 24.8.2015 15:16, Mel Gorman wrote:
return read_seqcount_retry(>mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled() &&
+ if (cpusets_mems_enabled() &&
(alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
static_key_count is an atomic read on a field in struct static_key where
as static_key_false is a arch_static_branch which can be eliminated. The
patch eliminates an atomic read so I didn't think it was moot.
Sorry I wasn't clear enough. My point is that AFAICS cpusets_enabled()
will only return true if there are more cpusets than the root
(top-level) one.
So the current cpusets_enabled() checks should be enough. Checking that
"nr_cpusets() > 1" only duplicates what is already covered by
cpusets_enabled() - see the nr_cpusets() listing above. I.e. David's
premise was wrong.
--
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
> On 24.8.2015 15:16, Mel Gorman wrote:
> >>>
> >>> return read_seqcount_retry(>mems_allowed_seq, seq);
> >>> @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t
> >>> nodemask)
> >>>
> >>> #else /* !CONFIG_CPUSETS */
> >>>
> >>> -static inline bool cpusets_enabled(void) { return false; }
> >>> +static inline bool cpusets_mems_enabled(void) { return false; }
> >>>
> >>> static inline int cpuset_init(void) { return 0; }
> >>> static inline void cpuset_init_smp(void) {}
> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> >>> index 62ae28d8ae8d..2c1c3bf54d15 100644
> >>> --- a/mm/page_alloc.c
> >>> +++ b/mm/page_alloc.c
> >>> @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
> >>> order, int alloc_flags,
> >>> if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
> >>> !zlc_zone_worth_trying(zonelist, z, allowednodes))
> >>> continue;
> >>> - if (cpusets_enabled() &&
> >>> + if (cpusets_mems_enabled() &&
> >>> (alloc_flags & ALLOC_CPUSET) &&
> >>> !cpuset_zone_allowed(zone, gfp_mask))
> >>> continue;
> >>
> >> Here the benefits are less clear. I guess cpuset_zone_allowed() is
> >> potentially costly...
> >>
> >> Heck, shouldn't we just start the static key on -1 (if possible), so that
> >> it's enabled only when there's 2+ cpusets?
>
> Hm wait a minute, that's what already happens:
>
> static inline int nr_cpusets(void)
> {
> /* jump label reference count + the top-level cpuset */
> return static_key_count(_enabled_key) + 1;
> }
>
> I.e. if there's only the root cpuset, static key is disabled, so I think this
> patch is moot after all?
>
static_key_count is an atomic read on a field in struct static_key where
as static_key_false is a arch_static_branch which can be eliminated. The
patch eliminates an atomic read so I didn't think it was moot.
--
Mel Gorman
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
On 24.8.2015 15:16, Mel Gorman wrote:
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t
nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(cpusets_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
static_key_count is an atomic read on a field in struct static_key where
as static_key_false is a arch_static_branch which can be eliminated. The
patch eliminates an atomic read so I didn't think it was moot.
--
Mel Gorman
SUSE Labs
--
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 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 08/25/2015 12:33 PM, Mel Gorman wrote:
On Mon, Aug 24, 2015 at 10:53:37PM +0200, Vlastimil Babka wrote:
On 24.8.2015 15:16, Mel Gorman wrote:
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(cpusets_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
static_key_count is an atomic read on a field in struct static_key where
as static_key_false is a arch_static_branch which can be eliminated. The
patch eliminates an atomic read so I didn't think it was moot.
Sorry I wasn't clear enough. My point is that AFAICS cpusets_enabled()
will only return true if there are more cpusets than the root
(top-level) one.
So the current cpusets_enabled() checks should be enough. Checking that
nr_cpusets() 1 only duplicates what is already covered by
cpusets_enabled() - see the nr_cpusets() listing above. I.e. David's
premise was wrong.
--
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 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 24.8.2015 15:16, Mel Gorman wrote:
>>>
>>> return read_seqcount_retry(>mems_allowed_seq, seq);
>>> @@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
>>>
>>> #else /* !CONFIG_CPUSETS */
>>>
>>> -static inline bool cpusets_enabled(void) { return false; }
>>> +static inline bool cpusets_mems_enabled(void) { return false; }
>>>
>>> static inline int cpuset_init(void) { return 0; }
>>> static inline void cpuset_init_smp(void) {}
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index 62ae28d8ae8d..2c1c3bf54d15 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
>>> order, int alloc_flags,
>>> if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
>>> !zlc_zone_worth_trying(zonelist, z, allowednodes))
>>> continue;
>>> - if (cpusets_enabled() &&
>>> + if (cpusets_mems_enabled() &&
>>> (alloc_flags & ALLOC_CPUSET) &&
>>> !cpuset_zone_allowed(zone, gfp_mask))
>>> continue;
>>
>> Here the benefits are less clear. I guess cpuset_zone_allowed() is
>> potentially costly...
>>
>> Heck, shouldn't we just start the static key on -1 (if possible), so that
>> it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
> It's overkill for the amount of benefit.
>
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Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon, Aug 24, 2015 at 02:37:41PM +0200, Vlastimil Babka wrote:
> >
> >+/* Returns true if a cpuset exists that can set cpuset.mems */
> >+static inline bool cpusets_mems_enabled(void)
> >+{
> >+return nr_cpusets() > 1;
> >+}
> >+
>
> Hm, but this loses the benefits of static key branches?
> How about something like:
>
> if (static_key_false(_enabled_key))
> return nr_cpusets() > 1
> else
> return false;
>
Will do.
>
>
> > static inline void cpuset_inc(void)
> > {
> > static_key_slow_inc(_enabled_key);
> >@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
> >task_struct *p);
> > */
> > static inline unsigned int read_mems_allowed_begin(void)
> > {
> >-if (!cpusets_enabled())
> >+if (!cpusets_mems_enabled())
> > return 0;
> >
> > return read_seqcount_begin(>mems_allowed_seq);
> >@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
> > */
> > static inline bool read_mems_allowed_retry(unsigned int seq)
> > {
> >-if (!cpusets_enabled())
> >+if (!cpusets_mems_enabled())
> > return false;
>
> Actually I doubt it's much of benefit for these usages, even if the static
> key benefits are restored. If there's a single root cpuset, we would check
> the seqlock prior to this patch, now we'll check static key value (which
> should have the same cost?). With >1 cpusets, we would check seqlock prior
> to this patch, now we'll check static key value *and* the seqlock...
>
If the cpuset is enabled between the check, it still should retry.
Anyway, special casing this is overkill. It's a small
micro-optimisation.
> >
> > return read_seqcount_retry(>mems_allowed_seq, seq);
> >@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
> >
> > #else /* !CONFIG_CPUSETS */
> >
> >-static inline bool cpusets_enabled(void) { return false; }
> >+static inline bool cpusets_mems_enabled(void) { return false; }
> >
> > static inline int cpuset_init(void) { return 0; }
> > static inline void cpuset_init_smp(void) {}
> >diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> >index 62ae28d8ae8d..2c1c3bf54d15 100644
> >--- a/mm/page_alloc.c
> >+++ b/mm/page_alloc.c
> >@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
> >order, int alloc_flags,
> > if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
> > !zlc_zone_worth_trying(zonelist, z, allowednodes))
> > continue;
> >-if (cpusets_enabled() &&
> >+if (cpusets_mems_enabled() &&
> > (alloc_flags & ALLOC_CPUSET) &&
> > !cpuset_zone_allowed(zone, gfp_mask))
> > continue;
>
> Here the benefits are less clear. I guess cpuset_zone_allowed() is
> potentially costly...
>
> Heck, shouldn't we just start the static key on -1 (if possible), so that
> it's enabled only when there's 2+ cpusets?
It's overkill for the amount of benefit.
--
Mel Gorman
SUSE Labs
--
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 08/24/2015 02:09 PM, Mel Gorman wrote:
David Rientjes correctly pointed out that the "root cpuset may not exclude
mems on the system so, even if mounted, there's no need to check or be
worried about concurrent change when there is only one cpuset".
The three checks for cpusets_enabled() care whether a cpuset exists that
can limit memory, not that cpuset is enabled as such. This patch replaces
cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
cpuset exists that can limit memory and updates the appropriate call sites.
Signed-off-by: Mel Gorman
---
include/linux/cpuset.h | 16 +---
mm/page_alloc.c| 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 6eb27cb480b7..1e823870987e 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,10 +17,6 @@
#ifdef CONFIG_CPUSETS
extern struct static_key cpusets_enabled_key;
-static inline bool cpusets_enabled(void)
-{
- return static_key_false(_enabled_key);
-}
static inline int nr_cpusets(void)
{
@@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
return static_key_count(_enabled_key) + 1;
}
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+ return nr_cpusets() > 1;
+}
+
Hm, but this loses the benefits of static key branches?
How about something like:
if (static_key_false(_enabled_key))
return nr_cpusets() > 1
else
return false;
static inline void cpuset_inc(void)
{
static_key_slow_inc(_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(>mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return false;
Actually I doubt it's much of benefit for these usages, even if the
static key benefits are restored. If there's a single root cpuset, we
would check the seqlock prior to this patch, now we'll check static key
value (which should have the same cost?). With >1 cpusets, we would
check seqlock prior to this patch, now we'll check static key value
*and* the seqlock...
return read_seqcount_retry(>mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled() &&
+ if (cpusets_mems_enabled() &&
(alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so
that it's enabled only when there's 2+ cpusets?
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
David Rientjes correctly pointed out that the "root cpuset may not exclude
mems on the system so, even if mounted, there's no need to check or be
worried about concurrent change when there is only one cpuset".
The three checks for cpusets_enabled() care whether a cpuset exists that
can limit memory, not that cpuset is enabled as such. This patch replaces
cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
cpuset exists that can limit memory and updates the appropriate call sites.
Signed-off-by: Mel Gorman
---
include/linux/cpuset.h | 16 +---
mm/page_alloc.c| 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 6eb27cb480b7..1e823870987e 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,10 +17,6 @@
#ifdef CONFIG_CPUSETS
extern struct static_key cpusets_enabled_key;
-static inline bool cpusets_enabled(void)
-{
- return static_key_false(_enabled_key);
-}
static inline int nr_cpusets(void)
{
@@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
return static_key_count(_enabled_key) + 1;
}
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+ return nr_cpusets() > 1;
+}
+
static inline void cpuset_inc(void)
{
static_key_slow_inc(_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(>mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return false;
return read_seqcount_retry(>mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) && zlc_active &&
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled() &&
+ if (cpusets_mems_enabled() &&
(alloc_flags & ALLOC_CPUSET) &&
!cpuset_zone_allowed(zone, gfp_mask))
continue;
--
2.4.6
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 08/24/2015 02:09 PM, Mel Gorman wrote:
David Rientjes correctly pointed out that the root cpuset may not exclude
mems on the system so, even if mounted, there's no need to check or be
worried about concurrent change when there is only one cpuset.
The three checks for cpusets_enabled() care whether a cpuset exists that
can limit memory, not that cpuset is enabled as such. This patch replaces
cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
cpuset exists that can limit memory and updates the appropriate call sites.
Signed-off-by: Mel Gorman mgor...@suse.de
---
include/linux/cpuset.h | 16 +---
mm/page_alloc.c| 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 6eb27cb480b7..1e823870987e 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,10 +17,6 @@
#ifdef CONFIG_CPUSETS
extern struct static_key cpusets_enabled_key;
-static inline bool cpusets_enabled(void)
-{
- return static_key_false(cpusets_enabled_key);
-}
static inline int nr_cpusets(void)
{
@@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
return static_key_count(cpusets_enabled_key) + 1;
}
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+ return nr_cpusets() 1;
+}
+
Hm, but this loses the benefits of static key branches?
How about something like:
if (static_key_false(cpusets_enabled_key))
return nr_cpusets() 1
else
return false;
static inline void cpuset_inc(void)
{
static_key_slow_inc(cpusets_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(current-mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return false;
Actually I doubt it's much of benefit for these usages, even if the
static key benefits are restored. If there's a single root cpuset, we
would check the seqlock prior to this patch, now we'll check static key
value (which should have the same cost?). With 1 cpusets, we would
check seqlock prior to this patch, now we'll check static key value
*and* the seqlock...
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so
that it's enabled only when there's 2+ cpusets?
--
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/
[PATCH 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
David Rientjes correctly pointed out that the root cpuset may not exclude
mems on the system so, even if mounted, there's no need to check or be
worried about concurrent change when there is only one cpuset.
The three checks for cpusets_enabled() care whether a cpuset exists that
can limit memory, not that cpuset is enabled as such. This patch replaces
cpusets_enabled() with cpusets_mems_enabled() which checks if at least one
cpuset exists that can limit memory and updates the appropriate call sites.
Signed-off-by: Mel Gorman mgor...@suse.de
---
include/linux/cpuset.h | 16 +---
mm/page_alloc.c| 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 6eb27cb480b7..1e823870987e 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -17,10 +17,6 @@
#ifdef CONFIG_CPUSETS
extern struct static_key cpusets_enabled_key;
-static inline bool cpusets_enabled(void)
-{
- return static_key_false(cpusets_enabled_key);
-}
static inline int nr_cpusets(void)
{
@@ -28,6 +24,12 @@ static inline int nr_cpusets(void)
return static_key_count(cpusets_enabled_key) + 1;
}
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+ return nr_cpusets() 1;
+}
+
static inline void cpuset_inc(void)
{
static_key_slow_inc(cpusets_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(current-mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
- if (!cpusets_enabled())
+ if (!cpusets_mems_enabled())
return false;
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
--
2.4.6
--
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 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On Mon, Aug 24, 2015 at 02:37:41PM +0200, Vlastimil Babka wrote:
+/* Returns true if a cpuset exists that can set cpuset.mems */
+static inline bool cpusets_mems_enabled(void)
+{
+return nr_cpusets() 1;
+}
+
Hm, but this loses the benefits of static key branches?
How about something like:
if (static_key_false(cpusets_enabled_key))
return nr_cpusets() 1
else
return false;
Will do.
static inline void cpuset_inc(void)
{
static_key_slow_inc(cpusets_enabled_key);
@@ -104,7 +106,7 @@ extern void cpuset_print_task_mems_allowed(struct
task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
-if (!cpusets_enabled())
+if (!cpusets_mems_enabled())
return 0;
return read_seqcount_begin(current-mems_allowed_seq);
@@ -118,7 +120,7 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
-if (!cpusets_enabled())
+if (!cpusets_mems_enabled())
return false;
Actually I doubt it's much of benefit for these usages, even if the static
key benefits are restored. If there's a single root cpuset, we would check
the seqlock prior to this patch, now we'll check static key value (which
should have the same cost?). With 1 cpusets, we would check seqlock prior
to this patch, now we'll check static key value *and* the seqlock...
If the cpuset is enabled between the check, it still should retry.
Anyway, special casing this is overkill. It's a small
micro-optimisation.
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
-if (cpusets_enabled()
+if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
It's overkill for the amount of benefit.
--
Mel Gorman
SUSE Labs
--
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 04/12] mm, page_alloc: Only check cpusets when one exists that can be mem-controlled
On 24.8.2015 15:16, Mel Gorman wrote:
return read_seqcount_retry(current-mems_allowed_seq, seq);
@@ -139,7 +141,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
#else /* !CONFIG_CPUSETS */
-static inline bool cpusets_enabled(void) { return false; }
+static inline bool cpusets_mems_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 62ae28d8ae8d..2c1c3bf54d15 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2470,7 +2470,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int
order, int alloc_flags,
if (IS_ENABLED(CONFIG_NUMA) zlc_active
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
- if (cpusets_enabled()
+ if (cpusets_mems_enabled()
(alloc_flags ALLOC_CPUSET)
!cpuset_zone_allowed(zone, gfp_mask))
continue;
Here the benefits are less clear. I guess cpuset_zone_allowed() is
potentially costly...
Heck, shouldn't we just start the static key on -1 (if possible), so that
it's enabled only when there's 2+ cpusets?
Hm wait a minute, that's what already happens:
static inline int nr_cpusets(void)
{
/* jump label reference count + the top-level cpuset */
return static_key_count(cpusets_enabled_key) + 1;
}
I.e. if there's only the root cpuset, static key is disabled, so I think this
patch is moot after all?
It's overkill for the amount of benefit.
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