[PATCH v2 0/2] memcg: variable type fixes

[PATCH v2 0/2] memcg: variable type fixes

[Greg Thelen]

This is a two part series that is a cleanup of memcg internal
counters.  These two patches were originally proposed by Johannes
Weiner [1].  The original series was based on an older mmotm, so I had
to massage the patches a little.  The patches are now based on
mmotm-2011-02-10-16-26.

Patch 1 implements the idea that memcg only has to use signed types
for some of the counters, but not for the constant monotonically
increasing event counters where the sign-bit is a waste.
Originally proposed in [2].
  
Patch 2 converts the memcg fundamental page statistics counters to
native words as they should be wide enough for the expected values.
Originally proposed in [3].

References:
  [1] https://lkml.org/lkml/2010/11/7/170
  [2] https://lkml.org/lkml/2010/11/7/174
  [3] https://lkml.org/lkml/2010/11/7/171

Johannes Weiner (2):
  memcg: break out event counters from other stats
  memcg: use native word page statistics counters

 mm/memcontrol.c |   78 ++++++++++++++++++++++++++++++++++++-------------------
 1 files changed, 51 insertions(+), 27 deletions(-)

-- 
1.7.3.1

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[PATCH v2 1/2] memcg: break out event counters from other stats

[Greg Thelen]

From: Johannes Weiner <hannes@cmpxchg.org>

For increasing and decreasing per-cpu cgroup usage counters it makes
sense to use signed types, as single per-cpu values might go negative
during updates.  But this is not the case for only-ever-increasing
event counters.

All the counters have been signed 64-bit so far, which was enough to
count events even with the sign bit wasted.

The next patch narrows the usage counters type (on 32-bit CPUs, that
is), though, so break out the event counters and make them unsigned
words as they should have been from the start.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Greg Thelen <gthelen@google.com>
---
Changelog since -v1:
* rebased to latest mmotm (including THP)

 mm/memcontrol.c |   49 +++++++++++++++++++++++++++++++++++++------------
 1 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b7e3379..a11ff1e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -93,19 +93,22 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
 	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as anon rss */
 	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
-	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
-	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
 	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
 	MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
-	/* incremented at every  pagein/pageout */
-	MEM_CGROUP_EVENTS = MEM_CGROUP_STAT_DATA,
 	MEM_CGROUP_ON_MOVE,	/* someone is moving account between groups */
-
 	MEM_CGROUP_STAT_NSTATS,
 };
 
+enum mem_cgroup_events_index {
+	MEM_CGROUP_EVENTS_PGPGIN,	/* # of pages paged in */
+	MEM_CGROUP_EVENTS_PGPGOUT,	/* # of pages paged out */
+	MEM_CGROUP_EVENTS_COUNT,	/* # of pages paged in/out */
+	MEM_CGROUP_EVENTS_NSTATS,
+};
+
 struct mem_cgroup_stat_cpu {
 	s64 count[MEM_CGROUP_STAT_NSTATS];
+	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
 };
 
 /*
@@ -577,6 +580,22 @@ static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
 	this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_SWAPOUT], val);
 }
 
+static unsigned long mem_cgroup_read_events(struct mem_cgroup *mem,
+					    enum mem_cgroup_events_index idx)
+{
+	unsigned long val = 0;
+	int cpu;
+
+	for_each_online_cpu(cpu)
+		val += per_cpu(mem->stat->events[idx], cpu);
+#ifdef CONFIG_HOTPLUG_CPU
+	spin_lock(&mem->pcp_counter_lock);
+	val += mem->nocpu_base.events[idx];
+	spin_unlock(&mem->pcp_counter_lock);
+#endif
+	return val;
+}
+
 static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
 					 bool file, int nr_pages)
 {
@@ -589,13 +608,13 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
 
 	/* pagein of a big page is an event. So, ignore page size */
 	if (nr_pages > 0)
-		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGIN_COUNT]);
+		__this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
 	else {
-		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGOUT_COUNT]);
+		__this_cpu_inc(mem->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
 		nr_pages = -nr_pages; /* for event */
 	}
 
-	__this_cpu_add(mem->stat->count[MEM_CGROUP_EVENTS], nr_pages);
+	__this_cpu_add(mem->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);
 
 	preempt_enable();
 }
@@ -617,9 +636,9 @@ static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
 
 static bool __memcg_event_check(struct mem_cgroup *mem, int event_mask_shift)
 {
-	s64 val;
+	unsigned long val;
 
-	val = this_cpu_read(mem->stat->count[MEM_CGROUP_EVENTS]);
+	val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]);
 
 	return !(val & ((1 << event_mask_shift) - 1));
 }
@@ -1747,6 +1766,12 @@ static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
 		per_cpu(mem->stat->count[i], cpu) = 0;
 		mem->nocpu_base.count[i] += x;
 	}
+	for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
+		unsigned long x = per_cpu(mem->stat->events[i], cpu);
+
+		per_cpu(mem->stat->events[i], cpu) = 0;
+		mem->nocpu_base.events[i] += x;
+	}
 	/* need to clear ON_MOVE value, works as a kind of lock. */
 	per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = 0;
 	spin_unlock(&mem->pcp_counter_lock);
@@ -3699,9 +3724,9 @@ mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
 	s->stat[MCS_RSS] += val * PAGE_SIZE;
 	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_FILE_MAPPED);
 	s->stat[MCS_FILE_MAPPED] += val * PAGE_SIZE;
-	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_PGPGIN_COUNT);
+	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGIN);
 	s->stat[MCS_PGPGIN] += val;
-	val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_PGPGOUT_COUNT);
+	val = mem_cgroup_read_events(mem, MEM_CGROUP_EVENTS_PGPGOUT);
 	s->stat[MCS_PGPGOUT] += val;
 	if (do_swap_account) {
 		val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
-- 
1.7.3.1

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Re: [PATCH v2 1/2] memcg: break out event counters from other stats

[KAMEZAWA Hiroyuki]

On Wed, 16 Feb 2011 21:34:01 -0800
Greg Thelen <gthelen@google.com> wrote:

> From: Johannes Weiner <hannes@cmpxchg.org>
> 
> For increasing and decreasing per-cpu cgroup usage counters it makes
> sense to use signed types, as single per-cpu values might go negative
> during updates.  But this is not the case for only-ever-increasing
> event counters.
> 
> All the counters have been signed 64-bit so far, which was enough to
> count events even with the sign bit wasted.
> 
> The next patch narrows the usage counters type (on 32-bit CPUs, that
> is), though, so break out the event counters and make them unsigned
> words as they should have been from the start.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Greg Thelen <gthelen@google.com>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

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Re: [PATCH v2 1/2] memcg: break out event counters from other stats

[KAMEZAWA Hiroyuki]

On Thu, 17 Feb 2011 14:33:15 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Wed, 16 Feb 2011 21:34:01 -0800
> Greg Thelen <gthelen@google.com> wrote:
> 
> > From: Johannes Weiner <hannes@cmpxchg.org>
> > 
> > For increasing and decreasing per-cpu cgroup usage counters it makes
> > sense to use signed types, as single per-cpu values might go negative
> > during updates.  But this is not the case for only-ever-increasing
> > event counters.
> > 
> > All the counters have been signed 64-bit so far, which was enough to
> > count events even with the sign bit wasted.
> > 
> > The next patch narrows the usage counters type (on 32-bit CPUs, that
> > is), though, so break out the event counters and make them unsigned
> > words as they should have been from the start.
> > 
> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: Greg Thelen <gthelen@google.com>
> 
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 

Hmm..but not mentioning the change "s64 -> unsigned long(may 32bit)" clearly
isn't good behavior. 

Could you clarify both of changes in patch description as
==
This patch
  - devides counters to signed and unsigned ones(increase only).
  - makes unsigned one to be 'unsigned long' rather than 'u64'
and
  - then next patch will make 'signed' part to be 'long'
==
for changelog ?

Thanks,
-Kame


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Re: [PATCH v2 1/2] memcg: break out event counters from other stats

[Greg Thelen]

On Wed, Feb 16, 2011 at 9:41 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Thu, 17 Feb 2011 14:33:15 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
>> On Wed, 16 Feb 2011 21:34:01 -0800
>> Greg Thelen <gthelen@google.com> wrote:
>>
>> > From: Johannes Weiner <hannes@cmpxchg.org>
>> >
>> > For increasing and decreasing per-cpu cgroup usage counters it makes
>> > sense to use signed types, as single per-cpu values might go negative
>> > during updates.  But this is not the case for only-ever-increasing
>> > event counters.
>> >
>> > All the counters have been signed 64-bit so far, which was enough to
>> > count events even with the sign bit wasted.
>> >
>> > The next patch narrows the usage counters type (on 32-bit CPUs, that
>> > is), though, so break out the event counters and make them unsigned
>> > words as they should have been from the start.
>> >
>> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
>> > Signed-off-by: Greg Thelen <gthelen@google.com>
>>
>> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>>
>
> Hmm..but not mentioning the change "s64 -> unsigned long(may 32bit)" clearly
> isn't good behavior.
>
> Could you clarify both of changes in patch description as
> ==
> This patch
>  - devides counters to signed and unsigned ones(increase only).
>  - makes unsigned one to be 'unsigned long' rather than 'u64'
> and
>  - then next patch will make 'signed' part to be 'long'
> ==
> for changelog ?
>
> Thanks,
> -Kame

Thanks for the review.

I will resent patches with the enhanced description.

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Re: [PATCH v2 1/2] memcg: break out event counters from other stats

[Balbir Singh]

* Greg Thelen <gthelen@google.com> [2011-02-16 21:34:01]:

> From: Johannes Weiner <hannes@cmpxchg.org>
> 
> For increasing and decreasing per-cpu cgroup usage counters it makes
> sense to use signed types, as single per-cpu values might go negative
> during updates.  But this is not the case for only-ever-increasing
> event counters.
> 
> All the counters have been signed 64-bit so far, which was enough to
> count events even with the sign bit wasted.
> 
> The next patch narrows the usage counters type (on 32-bit CPUs, that
> is), though, so break out the event counters and make them unsigned
> words as they should have been from the start.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Greg Thelen <gthelen@google.com>
> ---

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 
-- 
	Three Cheers,
	Balbir

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[PATCH v2 2/2] memcg: use native word page statistics counters

[Greg Thelen]

From: Johannes Weiner <hannes@cmpxchg.org>

The statistic counters are in units of pages, there is no reason to
make them 64-bit wide on 32-bit machines.

Make them native words.  Since they are signed, this leaves 31 bit on
32-bit machines, which can represent roughly 8TB assuming a page size
of 4k.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Greg Thelen <gthelen@google.com>
---
Changelog since -v1:
* rebased to latest mmotm

 mm/memcontrol.c |   29 ++++++++++++++---------------
 1 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a11ff1e..1c2704a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -107,7 +107,7 @@ enum mem_cgroup_events_index {
 };
 
 struct mem_cgroup_stat_cpu {
-	s64 count[MEM_CGROUP_STAT_NSTATS];
+	long count[MEM_CGROUP_STAT_NSTATS];
 	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
 };
 
@@ -546,11 +546,11 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
  * common workload, threashold and synchonization as vmstat[] should be
  * implemented.
  */
-static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
-		enum mem_cgroup_stat_index idx)
+static long mem_cgroup_read_stat(struct mem_cgroup *mem,
+				 enum mem_cgroup_stat_index idx)
 {
+	long val = 0;
 	int cpu;
-	s64 val = 0;
 
 	get_online_cpus();
 	for_each_online_cpu(cpu)
@@ -564,9 +564,9 @@ static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
 	return val;
 }
 
-static s64 mem_cgroup_local_usage(struct mem_cgroup *mem)
+static long mem_cgroup_local_usage(struct mem_cgroup *mem)
 {
-	s64 ret;
+	long ret;
 
 	ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
 	ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
@@ -1761,7 +1761,7 @@ static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
 
 	spin_lock(&mem->pcp_counter_lock);
 	for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
-		s64 x = per_cpu(mem->stat->count[i], cpu);
+		long x = per_cpu(mem->stat->count[i], cpu);
 
 		per_cpu(mem->stat->count[i], cpu) = 0;
 		mem->nocpu_base.count[i] += x;
@@ -3473,13 +3473,13 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
 }
 
 
-static u64 mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
-				enum mem_cgroup_stat_index idx)
+static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *mem,
+					       enum mem_cgroup_stat_index idx)
 {
 	struct mem_cgroup *iter;
-	s64 val = 0;
+	long val = 0;
 
-	/* each per cpu's value can be minus.Then, use s64 */
+	/* Per-cpu values can be negative, use a signed accumulator */
 	for_each_mem_cgroup_tree(iter, mem)
 		val += mem_cgroup_read_stat(iter, idx);
 
@@ -3499,12 +3499,11 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
 			return res_counter_read_u64(&mem->memsw, RES_USAGE);
 	}
 
-	val = mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE);
-	val += mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS);
+	val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
+	val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_RSS);
 
 	if (swap)
-		val += mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_SWAPOUT);
+		val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
 
 	return val << PAGE_SHIFT;
 }
-- 
1.7.3.1

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Re: [PATCH v2 2/2] memcg: use native word page statistics counters

[KAMEZAWA Hiroyuki]

On Wed, 16 Feb 2011 21:34:02 -0800
Greg Thelen <gthelen@google.com> wrote:

> From: Johannes Weiner <hannes@cmpxchg.org>
> 
> The statistic counters are in units of pages, there is no reason to
> make them 64-bit wide on 32-bit machines.
> 
> Make them native words.  Since they are signed, this leaves 31 bit on
> 32-bit machines, which can represent roughly 8TB assuming a page size
> of 4k.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Greg Thelen <gthelen@google.com>


Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>



> ---
> Changelog since -v1:
> * rebased to latest mmotm
> 
>  mm/memcontrol.c |   29 ++++++++++++++---------------
>  1 files changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a11ff1e..1c2704a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -107,7 +107,7 @@ enum mem_cgroup_events_index {
>  };
>  
>  struct mem_cgroup_stat_cpu {
> -	s64 count[MEM_CGROUP_STAT_NSTATS];
> +	long count[MEM_CGROUP_STAT_NSTATS];
>  	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
>  };
>  
> @@ -546,11 +546,11 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
>   * common workload, threashold and synchonization as vmstat[] should be
>   * implemented.
>   */
> -static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
> -		enum mem_cgroup_stat_index idx)
> +static long mem_cgroup_read_stat(struct mem_cgroup *mem,
> +				 enum mem_cgroup_stat_index idx)
>  {
> +	long val = 0;
>  	int cpu;
> -	s64 val = 0;
>  
>  	get_online_cpus();
>  	for_each_online_cpu(cpu)
> @@ -564,9 +564,9 @@ static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
>  	return val;
>  }
>  
> -static s64 mem_cgroup_local_usage(struct mem_cgroup *mem)
> +static long mem_cgroup_local_usage(struct mem_cgroup *mem)
>  {
> -	s64 ret;
> +	long ret;
>  
>  	ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
>  	ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
> @@ -1761,7 +1761,7 @@ static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
>  
>  	spin_lock(&mem->pcp_counter_lock);
>  	for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
> -		s64 x = per_cpu(mem->stat->count[i], cpu);
> +		long x = per_cpu(mem->stat->count[i], cpu);
>  
>  		per_cpu(mem->stat->count[i], cpu) = 0;
>  		mem->nocpu_base.count[i] += x;
> @@ -3473,13 +3473,13 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
>  }
>  
>  
> -static u64 mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
> -				enum mem_cgroup_stat_index idx)
> +static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *mem,
> +					       enum mem_cgroup_stat_index idx)
>  {
>  	struct mem_cgroup *iter;
> -	s64 val = 0;
> +	long val = 0;
>  
> -	/* each per cpu's value can be minus.Then, use s64 */
> +	/* Per-cpu values can be negative, use a signed accumulator */
>  	for_each_mem_cgroup_tree(iter, mem)
>  		val += mem_cgroup_read_stat(iter, idx);
>  
> @@ -3499,12 +3499,11 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
>  			return res_counter_read_u64(&mem->memsw, RES_USAGE);
>  	}
>  
> -	val = mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE);
> -	val += mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS);
> +	val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
> +	val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_RSS);
>  
>  	if (swap)
> -		val += mem_cgroup_get_recursive_idx_stat(mem,
> -				MEM_CGROUP_STAT_SWAPOUT);
> +		val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
>  
>  	return val << PAGE_SHIFT;
>  }
> -- 
> 1.7.3.1
> 
> 

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Re: [PATCH v2 2/2] memcg: use native word page statistics counters

[Balbir Singh]

* Greg Thelen <gthelen@google.com> [2011-02-16 21:34:02]:

> From: Johannes Weiner <hannes@cmpxchg.org>
> 
> The statistic counters are in units of pages, there is no reason to
> make them 64-bit wide on 32-bit machines.
> 
> Make them native words.  Since they are signed, this leaves 31 bit on
> 32-bit machines, which can represent roughly 8TB assuming a page size
> of 4k.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Greg Thelen <gthelen@google.com>


Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

-- 
	Three Cheers,
	Balbir

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