Re: userspace pagecache management tool

Ray Lee
2007-03-03T22:58:51Z

On 3/3/07, Andrew Morton <akpm@linux-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@phoenix:~/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@phoenix:~/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