[patch] mm, memcg: avoid unnecessary function call when memcg is disabled

Subsystems: control group - memory resource controller (memcg), memory management, the rest

STALE5037d

12 messages, 7 authors, 2012-11-29 · open the first message on its own page

[patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: David Rientjes <rientjes@google.com>
Date: 2012-11-20 01:44:39 

While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <redacted>
---
 include/linux/memcontrol.h |    9 ++++++++-
 mm/memcontrol.c            |    9 ++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 void mem_cgroup_split_huge_fixup(struct page *head);
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -59,6 +59,8 @@
 #include <trace/events/vmscan.h>
 
 struct cgroup_subsys mem_cgroup_subsys __read_mostly;
+EXPORT_SYMBOL(mem_cgroup_subsys);
+
 #define MEM_CGROUP_RECLAIM_RETRIES	5
 static struct mem_cgroup *root_mem_cgroup __read_mostly;
 
@@ -1015,13 +1017,10 @@ void mem_cgroup_iter_break(struct mem_cgroup *root,
 	     iter != NULL;				\
 	     iter = mem_cgroup_iter(NULL, iter, NULL))
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
 	struct mem_cgroup *memcg;
 
-	if (!mm)
-		return;
-
 	rcu_read_lock();
 	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
 	if (unlikely(!memcg))
@@ -1040,7 +1039,7 @@ void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 out:
 	rcu_read_unlock();
 }
-EXPORT_SYMBOL(mem_cgroup_count_vm_event);
+EXPORT_SYMBOL(__mem_cgroup_count_vm_event);
 
 /**
  * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg

Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Kamezawa Hiroyuki <hidden>
Date: 2012-11-20 04:23:56 

(2012/11/20 10:44), David Rientjes wrote:
While profiling numa/core v16 with cgroup_disable=memory on the command
line, I noticed mem_cgroup_count_vm_event() still showed up as high as
0.60% in perftop.

This occurs because the function is called extremely often even when memcg
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <redacted>
Acked-By: KAMEZAWA Hiroyuki <redacted>

Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Michal Hocko <hidden>
Date: 2012-11-20 07:07:33 

On Mon 19-11-12 17:44:34, David Rientjes wrote:
While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <redacted>

Thanks!
quoted hunk
---
 include/linux/memcontrol.h |    9 ++++++++-
 mm/memcontrol.c            |    9 ++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 void mem_cgroup_split_huge_fixup(struct page *head);
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -59,6 +59,8 @@
 #include <trace/events/vmscan.h>
 
 struct cgroup_subsys mem_cgroup_subsys __read_mostly;
+EXPORT_SYMBOL(mem_cgroup_subsys);
+
 #define MEM_CGROUP_RECLAIM_RETRIES	5
 static struct mem_cgroup *root_mem_cgroup __read_mostly;
 
@@ -1015,13 +1017,10 @@ void mem_cgroup_iter_break(struct mem_cgroup *root,
 	     iter != NULL;				\
 	     iter = mem_cgroup_iter(NULL, iter, NULL))
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
 	struct mem_cgroup *memcg;
 
-	if (!mm)
-		return;
-
 	rcu_read_lock();
 	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
 	if (unlikely(!memcg))
@@ -1040,7 +1039,7 @@ void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 out:
 	rcu_read_unlock();
 }
-EXPORT_SYMBOL(mem_cgroup_count_vm_event);
+EXPORT_SYMBOL(__mem_cgroup_count_vm_event);
 
 /**
  * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
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-- 
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SUSE Labs

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Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Glauber Costa <hidden>
Date: 2012-11-20 08:34:37 

On 11/20/2012 08:23 AM, Kamezawa Hiroyuki wrote:
(2012/11/20 10:44), David Rientjes wrote:
quoted
While profiling numa/core v16 with cgroup_disable=memory on the command
line, I noticed mem_cgroup_count_vm_event() still showed up as high as
0.60% in perftop.

This occurs because the function is called extremely often even when
memcg
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <redacted>
Acked-By: KAMEZAWA Hiroyuki <redacted>
I am fine with this as well.

Acked-by: Glauber Costa <redacted>

Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Johannes Weiner <hannes@cmpxchg.org>
Date: 2012-11-20 17:27:11 

On Mon, Nov 19, 2012 at 05:44:34PM -0800, David Rientjes wrote:
While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <redacted>
Acked-by: Johannes Weiner <redacted>

Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Andrew Morton <akpm@linux-foundation.org>
Date: 2012-11-20 21:49:35 

On Mon, 19 Nov 2012 17:44:34 -0800 (PST)
David Rientjes [off-list ref] wrote:
quoted hunk
While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

...

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
Does the !mm case occur frequently enough to justify inlining it, or
should that test remain out-of-line?

Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

From: Kamezawa Hiroyuki <hidden>
Date: 2012-11-21 01:03:00 

(2012/11/21 6:49), Andrew Morton wrote:
On Mon, 19 Nov 2012 17:44:34 -0800 (PST)
David Rientjes [off-list ref] wrote:
quoted
While profiling numa/core v16 with cgroup_disable=memory on the command
line, I noticed mem_cgroup_count_vm_event() still showed up as high as
0.60% in perftop.

This occurs because the function is called extremely often even when memcg
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the
unnecessary function call if memcg is disabled.

...

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
  						gfp_t gfp_mask,
  						unsigned long *total_scanned);

-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
Does the !mm case occur frequently enough to justify inlining it, or
should that test remain out-of-line?
I think this should be out-of-line.

Thanks,
-Kame

[patch] mm, memcg: avoid unnecessary function call when memcg is disabled fix

From: David Rientjes <rientjes@google.com>
Date: 2012-11-21 02:48:56 

Move the check for !mm out of line as suggested by Andrew.

Signed-off-by: David Rientjes <rientjes@google.com>
---
 include/linux/memcontrol.h |    2 +-
 mm/memcontrol.c            |    3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -185,7 +185,7 @@ void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
 static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
 					     enum vm_event_item idx)
 {
-	if (mem_cgroup_disabled() || !mm)
+	if (mem_cgroup_disabled())
 		return;
 	__mem_cgroup_count_vm_event(mm, idx);
 }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1021,6 +1021,9 @@ void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
 	struct mem_cgroup *memcg;
 
+	if (!mm)
+		return;
+
 	rcu_read_lock();
 	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
 	if (unlikely(!memcg))

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Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled fix

From: Kamezawa Hiroyuki <hidden>
Date: 2012-11-21 04:11:38 

(2012/11/21 11:48), David Rientjes wrote:
Move the check for !mm out of line as suggested by Andrew.

Signed-off-by: David Rientjes <redacted>
Thank you very much !

Acked-by: KAMEZAWA Hiroyuki <redacted>
quoted hunk
---
  include/linux/memcontrol.h |    2 +-
  mm/memcontrol.c            |    3 +++
  2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -185,7 +185,7 @@ void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
  static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
  					     enum vm_event_item idx)
  {
-	if (mem_cgroup_disabled() || !mm)
+	if (mem_cgroup_disabled())
  		return;
  	__mem_cgroup_count_vm_event(mm, idx);
  }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1021,6 +1021,9 @@ void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
  {
  	struct mem_cgroup *memcg;

+	if (!mm)
+		return;
+
  	rcu_read_lock();
  	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
  	if (unlikely(!memcg))





  

    
Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

    

      From: Michal Hocko <hidden>

      Date: 2012-11-21 08:35:24 
    

  

  
On Tue 20-11-12 13:49:32, Andrew Morton wrote:
On Mon, 19 Nov 2012 17:44:34 -0800 (PST)
David Rientjes [off-list ref] wrote:

quoted
While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

...

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
Does the !mm case occur frequently enough to justify inlining it, or
should that test remain out-of-line?
Now that you've asked about it I started looking around and I cannot see
how mm can ever be NULL. The condition is there since the very beginning
(456f998e memcg: add the pagefault count into memcg stats) but all the
callers are page fault handlers and those shouldn't have mm==NULL.
Or is there anything obvious I am missing?

Ying, the whole thread starts https://lkml.org/lkml/2012/11/19/545 but
the primary question is why we need !mm test for mem_cgroup_count_vm_event
at all.

Thanks!
-- 
Michal Hocko
SUSE Labs





  

    
Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled

    

      From: Hugh Dickins <hughd@google.com>

      Date: 2012-11-28 23:29:30 
    

  

  
On Wed, 21 Nov 2012, Michal Hocko wrote:
On Tue 20-11-12 13:49:32, Andrew Morton wrote:
quoted
On Mon, 19 Nov 2012 17:44:34 -0800 (PST)
David Rientjes [off-list ref] wrote:

quoted
While profiling numa/core v16 with cgroup_disable=memory on the command 
line, I noticed mem_cgroup_count_vm_event() still showed up as high as 
0.60% in perftop.

This occurs because the function is called extremely often even when memcg 
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the 
unnecessary function call if memcg is disabled.

...

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 						gfp_t gfp_mask,
 						unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
Does the !mm case occur frequently enough to justify inlining it, or
should that test remain out-of-line?
Now that you've asked about it I started looking around and I cannot see
how mm can ever be NULL. The condition is there since the very beginning
(456f998e memcg: add the pagefault count into memcg stats) but all the
callers are page fault handlers and those shouldn't have mm==NULL.
Or is there anything obvious I am missing?

Ying, the whole thread starts https://lkml.org/lkml/2012/11/19/545 but
the primary question is why we need !mm test for mem_cgroup_count_vm_event
at all.
Here's a guess: as Ying's 456f998e patch started out in akpm's tree,
shmem.c was calling mem_cgroup_count_vm_event(current->mm, PGMAJFAULT).

Then I insisted that was inconsistent with how we usually account when
one task touches another's address space, and rearranged it to work on
vma->vm_mm instead.

Done the original way, if the touching task were a kernel daemon (KSM's
ksmd comes to my mind), then the current->mm could well have been NULL.

I agree with you that it looks redundant now.

Hugh

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[PATCH] memcg: do not check for mm in mem_cgroup_count_vm_event disabled

    

      From: Michal Hocko <hidden>

      Date: 2012-11-29 13:29:01 
    

  

  
On Wed 28-11-12 15:29:30, Hugh Dickins wrote:
On Wed, 21 Nov 2012, Michal Hocko wrote:
quoted
On Tue 20-11-12 13:49:32, Andrew Morton wrote:
quoted
On Mon, 19 Nov 2012 17:44:34 -0800 (PST)
David Rientjes [off-list ref] wrote:
[...]
quoted
quoted
quoted
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+					     enum vm_event_item idx)
+{
+	if (mem_cgroup_disabled() || !mm)
+		return;
+	__mem_cgroup_count_vm_event(mm, idx);
+}
Does the !mm case occur frequently enough to justify inlining it, or
should that test remain out-of-line?
Now that you've asked about it I started looking around and I cannot see
how mm can ever be NULL. The condition is there since the very beginning
(456f998e memcg: add the pagefault count into memcg stats) but all the
callers are page fault handlers and those shouldn't have mm==NULL.
Or is there anything obvious I am missing?

Ying, the whole thread starts https://lkml.org/lkml/2012/11/19/545 but
the primary question is why we need !mm test for mem_cgroup_count_vm_event
at all.
Here's a guess: as Ying's 456f998e patch started out in akpm's tree,
shmem.c was calling mem_cgroup_count_vm_event(current->mm, PGMAJFAULT).

Then I insisted that was inconsistent with how we usually account when
one task touches another's address space, and rearranged it to work on
vma->vm_mm instead.
Thanks Hugh!
 
Done the original way, if the touching task were a kernel daemon (KSM's
ksmd comes to my mind), then the current->mm could well have been NULL.

I agree with you that it looks redundant now.
Andrew could you please pick this up?
---
From 619b1ab26c3e96944f6c60256cf7920671bafa5b Mon Sep 17 00:00:00 2001
From: Michal Hocko <redacted>
Date: Thu, 29 Nov 2012 14:20:58 +0100
Subject: [PATCH] memcg: do not check for mm in mem_cgroup_count_vm_event

mm given to mem_cgroup_count_vm_event cannot be NULL because the
function is either called from the page fault path or vma->vm_mm is
used. So the check can be dropped.

The check has been introduced by 456f998e (memcg: add the pagefault
count into memcg stats) because the originally proposed patch used
current->mm for shmem but this has been changed to vma->vm_mm later on
without the check being removed (thanks to Hugh for this recollection).

Signed-off-by: Michal Hocko <redacted>
---
 include/linux/memcontrol.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 095d2b4..0108a56 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -188,7 +188,7 @@ void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
 static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
 					     enum vm_event_item idx)
 {
-	if (mem_cgroup_disabled() || !mm)
+	if (mem_cgroup_disabled())
 		return;
 	__mem_cgroup_count_vm_event(mm, idx);
 }
-- 
1.7.10.4

-- 
Michal Hocko
SUSE Labs




    
  

  
    

      

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