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    SubjectRe: userspace pagecache management tool
    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
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