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Message-ID: <20070917163257.331c7605@twins>
Date: Mon, 17 Sep 2007 16:32:57 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Anton Altaparmakov <aia21@....ac.uk>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
marc.smith@...ail.mcc.edu
Subject: Re: VM/VFS bug with large amount of memory and file systems?
On Mon, 17 Sep 2007 15:04:05 +0100 Anton Altaparmakov <aia21@....ac.uk>
wrote:
> They files
> are attached this time rather than inlined so people don't complain
> about line wrapping! (No doubt people will not complain about them
> being attached! )-:)
I switched mailer after I learnt about flowed stuffs. Still,
appreciated.
> If I read it correctly it appears all of low memory is eaten up by
> buffer_heads.
>
> <quote>
> # name <active_objs> <num_objs> <objsize> <objperslab>
> <pagesperslab>
> : tunables <limit> <batchcount> <sharedfactor> : slabdata
> <active_slabs> <num_s
> labs> <sharedavail>
> buffer_head 12569528 12569535 56 67 1 : tunables
> 120 60 8 :
> slabdata 187605 187605 0
> </quote>
>
> That is 671MiB of low memory in buffer_heads.
>
> But why is the kernel not reclaiming them by getting rid of the page
> cache pages they are attached to or even leaving the pages around but
> killing their buffers?
Well, you see, you have this very odd configuration where:
11GB highmem
1GB normal
pagecache pages go into highmem
buggerheads go into normal
I'm guessing there is no pressure at all on zone_highmem so the
kernel will not try to reclaim pagecache. And because the pagecache
pages are happily sitting there, the buggerheads are pinned and do not
get reclaimed.
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