linux-kernel - Re: [PATCH mmotm] memcg use generic percpu allocator instead of private one

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Message-ID: <4B587317.6060404@linux.vnet.ibm.com>
Date:	Thu, 21 Jan 2010 21:00:31 +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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	kirill@...temov.name
Subject: Re: [PATCH mmotm] memcg use generic percpu allocator instead of private
 one

On Thursday 21 January 2010 07:37 AM, KAMEZAWA Hiroyuki wrote:
> On Wed, 20 Jan 2010 15:07:52 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
>>> This includes no functional changes.
>>>
>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>>
>> Before review, could you please post parallel pagefault data on a large
>> system, since root now uses these per cpu counters and its overhead is
>> now dependent on these counters. Also the data read from root cgroup is
>> also dependent on these, could you make sure that is not broken.
>>
> Hmm, I rewrote test program for avoidng mmap_sem. This version does fork()
> instead of pthread_create() and meausre parallel-process page fault speed.
> 
> [Before patch]
> [root@...extal memory]# /root/bin/perf stat -e page-faults,cache-misses --repeat 5 ./multi-fault-fork 8
> 
>  Performance counter stats for './multi-fault-fork 8' (5 runs):
> 
>        45256919  page-faults                ( +-   0.851% )
>       602230144  cache-misses               ( +-   0.187% )
> 
>    61.020533723  seconds time elapsed   ( +-   0.002% 
> 
> [After patch]
> [root@...extal memory]# /root/bin/perf stat -e page-faults,cache-misses --repeat 5 ./multi-fault-fork 8
> 
>  Performance counter stats for './multi-fault-fork 8' (5 runs):
> 
>        46007166  page-faults                ( +-   0.339% )
>       599553505  cache-misses               ( +-   0.298% )
> 
>    61.020937843  seconds time elapsed   ( +-   0.004% )
> 
> slightly improved ? But this test program does some extreme behavior and
> you can't see difference in real-world applications, I think.
> So, I guess this is in error-range in famous (not small) benchmarks.

Looks good, please give me a couple of days to test, I'll revert back
with numbers and review.

-- 
Three Cheers,
Balbir Singh
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