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From Greg Ames <grega...@remulak.net>
Subject Re: load spikes revisited
Date Fri, 18 Jan 2002 03:12:37 GMT
Greg Ames wrote:
> 
> I had 2.0.30-dev up briefly on daedalus tonight to collect doc on our load spike
> problem. 

> Anyway, there's about 20 seconds worth of ktrace output at
> http://www.apache.org/~gregames/ktrace.  We might have some kind of thundering
> herd problem - I see a whole bunch of unproductive context switches about the
> time a select pops.
> 
> Then I tried 2.0.29-dev from Nov. 15, with Ryan's patch to fix the timeouts on
> top of that.  That's got the load spikes as well, and that's not very long after
> we tagged 2_0_28.

Getting a lot closer.  httpd://www.apache.org/~gregames/ktrace.2_0_28 now has 30
some seconds of ktrace for comparison purposes.  Interestingly enough, this file
is considerably smaller than the 2.0.30-dev file which ran for less time. 
There's about twice the context switches in 2.0.30-dev's ktrace.

prefork was changed to do a apr_poll before the accept, even in the single
listen case, on Nov 10.  The polls seem to get added to the herd of selects that
wake up several times a second for no real good reason.  We need to get rid of
this poll once again.

Greg

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