Re: [PATCH 2/2] memcg: share event counter rather than duplicate

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 12 Feb 2010 16:40:18 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Fri, 12 Feb 2010 15:48:57 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > Memcg has 2 eventcountes which counts "the same" event. Just usages are
> > different from each other. This patch tries to reduce event counter.
> > 
> > This patch's logic uses "only increment, no reset" new_counter and masks for each
> > checks. Softlimit chesk was done per 1000 events. So, the similar check
> > can be done by !(new_counter & 0x3ff). Threshold check was done per 100
> > events. So, the similar check can be done by (!new_counter & 0x7f)
> > 
> > Cc: Kirill A. Shutemov <kirill@shutemov.name>
> > Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> > Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  mm/memcontrol.c |   36 ++++++++++++------------------------
> >  1 file changed, 12 insertions(+), 24 deletions(-)
> > 
> > Index: mmotm-2.6.33-Feb10/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-2.6.33-Feb10.orig/mm/memcontrol.c
> > +++ mmotm-2.6.33-Feb10/mm/memcontrol.c
> > @@ -63,8 +63,8 @@ static int really_do_swap_account __init
> >  #define do_swap_account		(0)
> >  #endif
> >  
> > -#define SOFTLIMIT_EVENTS_THRESH (1000)
> > -#define THRESHOLDS_EVENTS_THRESH (100)
> > +#define SOFTLIMIT_EVENTS_THRESH (0x3ff) /* once in 1024 */
> > +#define THRESHOLDS_EVENTS_THRESH (0x7f) /* once in 128 */
> >  
> >  /*
> >   * Statistics for memory cgroup.
> > @@ -79,10 +79,7 @@ enum mem_cgroup_stat_index {
> >  	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_SOFTLIMIT, /* decrements on each page in/out.
> > -					used by soft limit implementation */
> > -	MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
> > -					used by threshold implementation */
> > +	MEM_CGROUP_EVENTS,	/* incremented by 1 at pagein/pageout */
> >  
> >  	MEM_CGROUP_STAT_NSTATS,
> >  };
> > @@ -394,16 +391,12 @@ mem_cgroup_remove_exceeded(struct mem_cg
> >  
> >  static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
> >  {
> > -	bool ret = false;
> >  	s64 val;
> >  
> > -	val = this_cpu_read(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT]);
> > -	if (unlikely(val < 0)) {
> > -		this_cpu_write(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT],
> > -				SOFTLIMIT_EVENTS_THRESH);
> > -		ret = true;
> > -	}
> > -	return ret;
> > +	val = this_cpu_read(mem->stat->count[MEM_CGROUP_EVENTS]);
> > +	if (unlikely(!(val & SOFTLIMIT_EVENTS_THRESH)))
> > +		return true;
> > +	return false;
> >  }
> >  
> >  static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
> > @@ -542,8 +535,7 @@ static void mem_cgroup_charge_statistics
> >  		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGIN_COUNT]);
> >  	else
> >  		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGOUT_COUNT]);
> > -	__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT]);
> > -	__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS]);
> > +	__this_cpu_dec(mem->stat->count[MEM_CGROUP_EVENTS]);
> >
> I think using __this_cpu_inc() would be more natural(and the patch description
> says "increment" :)).
> 
yes...yes..will post v2.

Thanks,
-Kame


> Thanks,
> Daisuke Nishimura.
> 
> >  	preempt_enable();
> >  }
> > @@ -3211,16 +3203,12 @@ static int mem_cgroup_swappiness_write(s
> >  
> >  static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
> >  {
> > -	bool ret = false;
> >  	s64 val;
> >  
> > -	val = this_cpu_read(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS]);
> > -	if (unlikely(val < 0)) {
> > -		this_cpu_write(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS],
> > -				THRESHOLDS_EVENTS_THRESH);
> > -		ret = true;
> > -	}
> > -	return ret;
> > +	val = this_cpu_read(mem->stat->count[MEM_CGROUP_EVENTS]);
> > +	if (unlikely(!(val & THRESHOLDS_EVENTS_THRESH)))
> > +		return true;
> > +	return false;
> >  }
> >  
> >  static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
> > 
> 

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