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    SubjectRe: 2.6.18-rc3-mm2 - OOM storm
    On Thu, 10 Aug 2006 11:04:36 +0200
    Laurent Riffard <laurent.riffard@free.fr> wrote:

    > Le 06.08.2006 12:08, Andrew Morton a écrit :
    > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.18-rc3/26.18-rc3-mm2/
    >
    > Hello,
    >
    > On my system, a cron runs every day to check the integrity of
    > installed RPMS, it runs "rpm -v" on each package, which computes
    > MD5 hash for each installed file and compares this result, the file
    > size and modification time with values stored in RPM database.
    >
    > This is the workload. Since 2.6.18-rc3-mm2, this processus eats
    > all the memory and triggers OOM.
    >
    > On my system, "free -t" output normally looks like this ("cached" value
    > is about half of RAM):
    > # free -t
    > total used free shared buffers cached
    > Mem: 515032 508512 6520 0 22992 256032
    > -/+ buffers/cache: 229488 285544
    > Swap: 1116428 324 1116104
    > Total: 1631460 508836 1122624
    >
    > After the rpm database check, "free -t" says:
    > total used free shared buffers cached
    > Mem: 515032 507124 7908 0 8132 398296
    > -/+ buffers/cache: 100696 414336
    > Swap: 1116428 34896 1081532
    > Total: 1631460 542020 1089440
    >
    > And the value of "cached" won't decrease.
    >

    Yes, I was just trying to reproduce this. No luck so far. Will try your
    .config tomorrow.

    It would be interesting to try disabling CONFIG_ADAPTIVE_READAHEAD -
    perhaps that got broken.

    Also, are you able to determine whether the problem is specific to `rpm
    -V'? Are you able to make the leak trigger using other filesystem
    workloads?

    If it's specific to `rpm -V' then perhaps direct-io is somehow causing
    pagecache leakage. That would be a bit odd.



    btw, it's not necessary to go all the way to oom to work out if the
    pagecache leak is happening. After booting, do

    echo 3 > /proc/sys/vm/drop_pagecache

    and record the `Cached' figure in /proc/meminfo. After running some test,
    run `echo 3 > /proc/sys/vm/drop_pagecache' again and check
    /proc/meminfo:Cached. If it dodn't do gown to a similarly low figure,
    we're leaking pagecache.

    btw2: please use /proc/meminfo output rather than free(1). Because free(1)
    shows less info, and it does mysterious mangling of the info which it does
    read in ways which confuse me.

    Thanks.

    -
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