From: Victor Duchovni (Victor.DuchovniMorganStanley.com)
Date: Thu Nov 01 2007 - 09:40:38 CDT

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On Thu, Nov 01, 2007 at 07:34:35AM -0700, Andreas Grimm wrote:

> Hello Wietse,
>
> that was the perfect hint. Load is now about 200 under stress (before
> 2 to 3 because of the stalled smptds), server answers immediately, even
> under that conditions. The only thing i've done, was to shut down the
> syslog. Synchronous log was turned off, of course. It's syslog-ng, so the
> paremeter is sync(0), but that doesn't helped here. I should try now to
> tune my syslog-ng (maybe the break is log_fifo_size) or install the normal
> syslog-package. Maybe that's an interesting addon for the stress readme.

Are you using "unix-stream" or "unix-dgram"? The former does not scale.
You MUST use "unix-dgram" for syslog on busy (really all) Postfix
servers:

    source local {
        pipe("/proc/kmsg");
        unix-dgram("/dev/log");
        internal();
    };

With a stream socket each process has a separate connection to the
syslog-ng daemon, and it simply can't handle thousands of connections.

--
        Viktor.

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