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From Greg Ames <>
Subject Re: 2.0.29 high load avg
Date Wed, 09 Jan 2002 19:46:50 GMT
Brian Pane wrote:
> Can someone describe what the difference is between the select/accept/mutex
> behavior of .28 and .29/.30 on daedalus?

There shouldn't be any differences theoretically, and I haven't found any
accidental ones yet either.  

However there were changes in that time period which moved the client socket out
of the conn_rec.  This changed things like the mechanism to set read timeouts,
and lingering close.  The resulting syscalls _should_ be identical AFAIK.

I was considering creating a build from a date checkout prior to when these
changes started.  But that was the same day 2_0_28 was rolled (Nov 12), so it
wouldn't prove a whole lot if it worked.
> Also, do we have any data on syscalls per request during the spikes?
> Based on Greg's vmstat data showing a spike in syscalls/second concurrent
> with the spike in load, I'd
> expect that either:
>   * The number of requests/second increased, or
>   * The number of syscalls/request increased

That's a very interesting question.  I wish I could give you a good answer.  Is
there some function that returns the total number of syscalls a process has
done?  If so, we could create a patch to log the delta in the number of syscalls
at the end of each request, like I'm doing for cpu ticks now.

btw, if the connection dies during ap_read_request, the request isn't logged,
and my current patch will loose any cpu time burned during the reading and error


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