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From: Arun Sharma <asharma@fb.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Balbir Singh <bsingharora@gmail.com>,
	akpm@linux-foundation.org
Subject: Re: [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu
Date: Tue, 24 Jan 2012 17:45:28 -0800	[thread overview]
Message-ID: <4F1F5EB8.3000407@fb.com> (raw)
In-Reply-To: <20120124120704.3f09b206.kamezawa.hiroyu@jp.fujitsu.com>

On 1/23/12 7:07 PM, KAMEZAWA Hiroyuki wrote:

> You can see reduction of clear_page() cost by removing GFP_ZERO but
> what's your application's total performance ? Is it good enough considering
> many risks ?

I see 90k calls/sec to clear_page_c when running our application. I 
don't have data on the impact of GFP_ZERO alone, but an earlier 
experiment when we tuned malloc to not call madvise(MADV_DONTNEED) 
aggressively saved us 3% CPU. So I'm expecting this to be a 1-2% win.

But not calling madvise() increases our RSS and increases the risk of OOM.

Agree with your analysis that removing the cache misses at clear_page() 
is not always a win, since it moves the misses to the code where the app 
first touches the data.

  -Arun


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  reply	other threads:[~2012-01-25  1:45 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-18 18:51 [PATCH] mm: Enable MAP_UNINITIALIZED for archs with mmu Arun Sharma
2012-01-19  2:42 ` KAMEZAWA Hiroyuki
2012-01-24  0:54   ` Arun Sharma
2012-01-24  3:07     ` KAMEZAWA Hiroyuki
2012-01-25  1:45       ` Arun Sharma [this message]
2012-02-22  0:34         ` Arun Sharma
2012-02-23  7:45 ` Balbir Singh
2012-02-23 18:42   ` Arun Sharma
2012-02-24  2:47     ` KAMEZAWA Hiroyuki
2012-02-24 14:51       ` Balbir Singh
2012-02-24 19:11         ` Arun Sharma
2012-02-25  4:13           ` Balbir Singh
2012-02-27 18:32             ` Arun Sharma
2012-02-24 19:26       ` Arun Sharma

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