[Devel] Re: [PATCH v5 3/4] memcg: rework usage of stats by soft limit

[KAMEZAWA Hiroyuki]

On Wed, 30 Dec 2009 17:57:58 +0200
"Kirill A. Shutemov" <kirill at shutemov.name> wrote:

> Instead of incrementing counter on each page in/out and comparing it
> with constant, we set counter to constant, decrement counter on each
> page in/out and compare it with zero. We want to make comparing as fast
> as possible. On many RISC systems (probably not only RISC) comparing
> with zero is more effective than comparing with a constant, since not
> every constant can be immediate operand for compare instruction.
> 
> Also, I've renamed MEM_CGROUP_STAT_EVENTS to MEM_CGROUP_STAT_SOFTLIMIT,
> since really it's not a generic counter.
> 
> Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
> 
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>

> ---
> 
> KAMEZAWA-san, I've changed the patch a bit. Can I reuse your Acked-by?
> 
> ---
>  mm/memcontrol.c |   18 ++++++++++--------
>  1 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1d71cb4..c36d4f3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -69,8 +69,9 @@ enum mem_cgroup_stat_index {
>  	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_EVENTS,	/* sum of pagein + pageout for internal use */
>  	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_NSTATS,
>  };
> @@ -84,10 +85,10 @@ struct mem_cgroup_stat {
>  };
>  
>  static inline void
> -__mem_cgroup_stat_reset_safe(struct mem_cgroup_stat_cpu *stat,
> -				enum mem_cgroup_stat_index idx)
> +__mem_cgroup_stat_set_safe(struct mem_cgroup_stat_cpu *stat,
> +				enum mem_cgroup_stat_index idx, s64 val)
>  {
> -	stat->count[idx] = 0;
> +	stat->count[idx] = val;
>  }
>  
>  static inline s64
> @@ -380,9 +381,10 @@ static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
>  
>  	cpu = get_cpu();
>  	cpustat = &mem->stat.cpustat[cpu];
> -	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
> -	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
> -		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
> +	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_SOFTLIMIT);
> +	if (unlikely(val < 0)) {
> +		__mem_cgroup_stat_set_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT,
> +				SOFTLIMIT_EVENTS_THRESH);
>  		ret = true;
>  	}
>  	put_cpu();
> @@ -515,7 +517,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
>  	else
>  		__mem_cgroup_stat_add_safe(cpustat,
>  				MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
> -	__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_EVENTS, 1);
> +	__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);
>  	put_cpu();
>  }
>  
> -- 
> 1.6.5.7
> 
> 

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