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    SubjectRe: Maybe a VM bug in 2.4.18-18 from RH 8.0?
    Norman Gaywood wrote:
    >
    > I think I have a trigger for a VM bug in the RH kernel-bigmem-2.4.18-18
    >
    > 16GB
    > ...
    > tar cf /dev/tape .
    >

    This machine will die due to buffer_heads which are attached
    to highmem pagecache, and due to inodes which are pinned by
    highmem pagecache.

    > ...
    > while [ `expr $COUNT - 1` != 0 ]
    > do
    > date
    > # 2000 by 1_000_000 seems to be a 1.8G process
    > perl -e '$i=2000;while ($i--){ $a[$i]="x"x1_000_000; }' &
    > ...

    This will evict the highmem pagecache. That frees the buffer_heads
    and unpins the inodes.

    > So what do I do now?

    I guess talk to Red Hat. These are well-known problems and there
    should be fixes for them in a "bigmem" kernel.

    Otherwise, the -aa kernels have patches to address these problems.
    One option would be to roll your own kernel, based on a kernel.org
    kernel and a matching patch from
    http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/

    > ...
    > Anyone have some patches for me to
    > try that won't take me too far from the RH 8.0 base system.

    Hard. The relevant patches are:

    http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.20aa1/05_vm_16_active_free_zone_bhs-1
    and
    http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.20aa1/10_inode-highmem-2

    The first one will not come vaguely close to applying to an
    RH 2.4.18 kernel.

    The second one may well apply, and will probably fix the problem.
    -
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