linux-kernel - Re: Very aggressive memory reclaim

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Message-ID: <20110328174250.GE8529@home.goodmis.org>
Date:	Mon, 28 Mar 2011 13:42:50 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	John Lepikhin <johnlepikhin@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org
Subject: Re: Very aggressive memory reclaim

[ Add Cc's of those that may help you ]

-- Steve

On Mon, Mar 28, 2011 at 08:39:29PM +0400, John Lepikhin wrote:
> Hello,
> 
> I use high-loaded machine with 10M+ inodes inside XFS, 50+ GB of
> memory, intensive HDD traffic and 20..50 forks per second. Vanilla
> kernel 2.6.37.4. The problem is that kernel frees memory very
> aggressively.
> 
> For example:
> 
> 25% of memory is used by processes
> 50% for page caches
> 7% for slabs, etc.
> 18% free.
> 
> That's bad but works. After few hours:
> 
> 25% of memory is used by processes
> 62% for page caches
> 7% for slabs, etc.
> 5% free.
> 
> Most of files are cached, works perfectly. This is the moment when
> kernel decides to free some memory. After memory reclaim:
> 
> 25% of memory is used by processes
> 25% for page caches(!)
> 7% for slabs, etc.
> 43% free(!)
> 
> Page cache is dropped, server becomes too slow. This is the beginning
> of new cycle.
> 
> I didn't found any huge mallocs at that moment. Looks like because of
> large number of small mallocs (forks) kernel have pessimistic forecast
> about future memory usage and frees too much memory. Is there any
> options of tuning this? Any other variants?
> 
> Thanks!
> --
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