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    SubjectRe: BUG: Slowdown on 3000 socket-machines tracked down
    Willy Tarreau wrote:
    > On Mon, Mar 07, 2005 at 04:14:37PM +1100, Nick Piggin wrote:
    >>I think you would have better luck in reproducing this problem if you
    >>did the full sendfile thing.
    >>I think it is becoming disk bound due to page reclaim problems, which
    >>is causing the slowdown.
    >>In that case, writing the network only test would help to confirm the
    >>problem is not a networking one - so not useless by any means.
    > Not necessarily, Nick. I have written an HTTP testing tool which matches
    > the description of Ben's : non-blocking, single-threaded, no disk I/O,
    > etc... It works flawlessly under 2.4, and gives me random numbers in 2.6,

    No you're right, I'm not 100% sure, so I'm definitely not saying
    Ben's test will be useless. Just that if it is not too hard to
    make one with sendfile, I think he should.

    If he makes a network-only version and cannot reproduce the problems,
    that *doesn't* mean it is *not* a network problem. However if he
    reproduces the problem with a full sendfile version and not the network
    only one, then that is a better indicator... but I'm rambling.

    > especially if I start some CPU activity on the system, I can get pauses
    > of up to 13 seconds without this tool doing anything !!! At first I
    > believed it was because of the scheduler, but it might also be related
    > to what is described here since I had somewhat the same setup (gigE, 1500,
    > thousands of sockets). I never had enough time to investigate more, so I
    > went back to 2.4.

    I have heard other complaints about this, and they are definitely
    related to the scheduler (not saying yours is, but it is very possible).

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