linux-kernel - Re: [PATCH 6/12] memcg optimize percpu stat

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Message-ID: <48DCB107.1020307@linux.vnet.ibm.com>
Date:	Fri, 26 Sep 2008 15:23:11 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"xemul@...nvz.org" <xemul@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Hansen <haveblue@...ibm.com>, ryov@...inux.co.jp
Subject: Re: [PATCH 6/12] memcg optimize percpu stat

KAMEZAWA Hiroyuki wrote:
> Some obvious optimization to memcg.
> 
> I found mem_cgroup_charge_statistics() is a little big (in object) and
> does unnecessary address calclation.
> This patch is for optimization to reduce the size of this function.
> 
> And res_counter_charge() is 'likely' to success.
> 
> Changelog v3->v4:
>  - merged with an other leaf patch.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
>  mm/memcontrol.c |   18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> Index: mmotm-2.6.27-rc7+/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.27-rc7+.orig/mm/memcontrol.c
> +++ mmotm-2.6.27-rc7+/mm/memcontrol.c
> @@ -66,11 +66,10 @@ struct mem_cgroup_stat {
>  /*
>   * For accounting under irq disable, no need for increment preempt count.
>   */
> -static void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat *stat,
> +static inline void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat_cpu *stat,
>  		enum mem_cgroup_stat_index idx, int val)
>  {
> -	int cpu = smp_processor_id();
> -	stat->cpustat[cpu].count[idx] += val;
> +	stat->count[idx] += val;
>  }
> 
>  static s64 mem_cgroup_read_stat(struct mem_cgroup_stat *stat,
> @@ -237,18 +236,21 @@ static void mem_cgroup_charge_statistics
>  {
>  	int val = (charge)? 1 : -1;
>  	struct mem_cgroup_stat *stat = &mem->stat;
> +	struct mem_cgroup_stat_cpu *cpustat;
> 
>  	VM_BUG_ON(!irqs_disabled());
> +
> +	cpustat = &stat->cpustat[smp_processor_id()];
>  	if (PageCgroupCache(pc))
> -		__mem_cgroup_stat_add_safe(stat, MEM_CGROUP_STAT_CACHE, val);
> +		__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_CACHE, val);
>  	else
> -		__mem_cgroup_stat_add_safe(stat, MEM_CGROUP_STAT_RSS, val);
> +		__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_RSS, val);
> 
>  	if (charge)
> -		__mem_cgroup_stat_add_safe(stat,
> +		__mem_cgroup_stat_add_safe(cpustat,
>  				MEM_CGROUP_STAT_PGPGIN_COUNT, 1);
>  	else
> -		__mem_cgroup_stat_add_safe(stat,
> +		__mem_cgroup_stat_add_safe(cpustat,
>  				MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
>  }
> 
> @@ -609,7 +611,7 @@ static int mem_cgroup_charge_common(stru
>  		css_get(&memcg->css);
>  	}
> 
> -	while (res_counter_charge(&mem->res, PAGE_SIZE)) {
> +	while (unlikely(res_counter_charge(&mem->res, PAGE_SIZE))) {
>  		if (!(gfp_mask & __GFP_WAIT))
>  			goto out;
> 
> 

Looks good to me

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

-- 
	Balbir
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