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    SubjectRe: 2.6.26.3 kernel - progressive slowdown over NFS
    Date
    On 2008-09-10, Priyank Patel <pkpatel.lists@gmail.com> wrote:
    > We have a simple python program which keeps running a C loop to lstat
    > NFS mounted directories. We are seeing some weird behavior w.r.t. the
    > run-time of this program on 2.6.26.3 kernel vs 2.6.24 kernel.
    >
    > The run-time of the following code increases over time on the 2.6.26.3
    > kernel, whereas remains flat (as expected) on the 2.6.24 kernel.

    I'm seeing a similar effect, and ran a benchmark pre and post reboot:

    $ strace -T /usr/sbin/bonnie++ -d . -s 0 -f -n 1 >/tmp/bonnie-r44237-netslow 2>&1
    ...reboot...
    $ strace -T /usr/sbin/bonnie++ -d . -s 0 -f -n 1 >/tmp/bonnie-r44237-netfast 2>&1

    Graphs of the operations are avaliable:
    http://davidf.woaf.net/nfsfail-2.6.26/

    In particular http://davidf.woaf.net/nfsfail-2.6.26/r44237-stat.pdf

    r44237-* was a machine with a 28 day uptime and
    r44088-* is an identical machine with 14 day uptime.

    The graphs show times as recorded by strace for each syscall (points), a
    cumulative frequency plot is also drawn on the same graph (lines).
    yellow-orange points/lines are before the reboot, purple afterwards.

    The machines are part of a cluster with a r/o nfsroot and common debian
    stock kernel:
    Linux r44088 2.6.26-1-amd64 #1 SMP Sat Aug 2 11:15:08 GMT 2008 x86_64 GNU/Linux

    Other nfs filesystems are also mounted; all nfs mounts are nfsv3 over udp.

    Has this issue been identified or resolved in 2.6.27?

    Extra logs can be provided if required.

    ..david



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