linux-kernel - Re: userspace pagecache management tool

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Date:	Sat, 3 Mar 2007 14:58:48 -0800
From:	"Ray Lee" <madrabbit@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: userspace pagecache management tool

On 3/3/07, Andrew Morton <akpm@...ux-foundation.org> wrote:
> It is to address the "waah, backups fill my memory with pagecache" and the
> "waah, updatedb swapped everything out" and the "waah, copying a DVD
> gobbled all my memory" problems.

Is the updatedb problem really due to pagecache?

> When running
>
>         pagecache-management.sh dd if=100-mb-file of=foo
>         or
>         pagecache-management.sh cp -a /usr/src/linux-2.6.20 /usr/src/foo
>
> the amount of pagecache in the machine is pretty much unaltered.  Maybe a
> megabyte of additional cache in the second case, because of ext3 indirect
> blocks.

ray@...enix:~/work/home/pagecache-management$ grep ext3_i
/proc/slabinfo; ./pagecache-management.sh sudo updatedb; grep ext3_i
/proc/slabinfo
ext3_inode_cache   21024  23722   1584    2    1 : tunables   24   12
  0 : slabdata  11861  11861      0
ext3_inode_cache   41332  41332   1584    2    1 : tunables   24   12
  0 : slabdata  20666  20666      0
ray@...enix:~/work/home/pagecache-management$ echo $(( 1584 * (41332-21024) ))
32167872

Or is there a /proc/sys/vm/* knob that can be tweaked for this
before/after the updatedb?

But yeah, I for one would happily submit patches to upstream authors
to address this there. There's no reason code should be making the
kernel guess its intention on these things.

Ray
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