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    SubjectRe: What's the NFS OOM problem?
    Neil Brown wrote:
    > On Tuesday August 15, wrote:
    >> I have noticed on SLES kernels that when the dirty_*ratios turned down it
    >> still uses alot more memory than it should work writeback buffers, it makes
    >> me think that with the default setting of 40% that it for some reason
    >> may be using all of memory and deadlocking. It does not seem like an
    >> NFS only issue, as I believe I have duplicated it with a fast lock
    >> setup.
    > We seem to have a little patch in SuSE kernels that might be making
    > the problem worse .... though I presume it was introduced for a
    > reason. I haven't managed to track what that reason was yet.
    > What is "a fast lock setup"?? I don't understand.
    > NeilBrown

    I am not sure what I ment, I may have ment a fast disk setup, and
    thought or typed the wrong thing. The machine I duplicated it with
    had disks that would sustain 175MB/second (3 striped), 4cpus with local
    ram of 32GB. The 2 cpu/4GB/100MB/second machine does not seem
    to have the issue. Both machines are opterons, I believe I duplicated
    it under SP2, I know I duplicated it SP3 and one of the
    post-SP3 kernels. It did not occur under SP1.

    Turning down the dirty*ratios seems to make it go away. When I
    get a chance I will retest on SP2 and see if it happens there.

    I do know (and this may be related) that if on a 32GB machine I
    pagelock a large portion of ram (say 28GB) that machine will deadlock
    under high IO. The basic symptoms are similar to the writeback
    issue the machine responds to ping/sysrq, but logins fail, and any
    new process creation fails.

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      Last update: 2006-08-17 15:47    [W:0.021 / U:12.084 seconds]
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