linux-kernel - Re: [BUG?] vfs_cache_pressure=0 does not free inode caches

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Message-ID: <20100510172621.284310@gmx.net>
Date:	Mon, 10 May 2010 19:26:21 +0200
From:	"Alexander Stohr" <Alexander.Stohr@....de>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...l.org, trond.myklebust@....uio.no, riel@...hat.com,
	major@...x.net
Subject: Re: [BUG?] vfs_cache_pressure=0 does not free inode caches

this is a follow up to:
http://lkml.indiana.edu/hypermail/linux/kernel/0904.1/03026.html

> The server is going to die a slow death,
> all user space memory is swapped out,
> then all processes are OOM killed 
> until it dies from complete memory exhaustion."

> a cache is supposed to be a cache and not a memory hog

i'm running an embedded system with NFS as my working area.
the system has only few ram leftover, any MiBi counts.

my current best guess to resolve low memory situations
is a manual one (no, i could not see any smart kernel reaction
with that relatively old but patched 2.6.18 kernel) is this:

echo 100000 >/proc/sys/vm/vfs_cache_pressure
sync
echo 1 >/proc/sys/vm/drop_caches
echo 2 >/proc/sys/vm/drop_caches

any hints on that?
is this still an issue in current kernels
or is this already addressed in some way?

regards, Alex.


here is the link to the initial patch set applied to 2.6.8:
http://git.kernel.org/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=95afb3658a8217ff2c262e202601340323ef2803

some other people spotting similar effects:
http://rackerhacker.com/2008/12/03/reducing-inode-and-dentry-caches-to-keep-oom-killer-at-bay/
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