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From Brian Pane <brian.p...@cnet.com>
Subject Re: load spikes due to lingering close?
Date Wed, 09 Jan 2002 07:52:56 GMT
Justin Erenkrantz wrote:

>Well, first off, here are some kdumps on this:
>
>http://www.apache.org/~jerenkrantz/freebsd/
>
>ktrace.dump.abs.gz - kdump'd output with absolute timestamps
>ktrace.dump.rel.gz - kdump'd output with relative timestamps
>ktrace.out.gz      - raw ktrace file
>

Can you clarify what it is that these traces are supposed to
show?  Was there a spike in load during the middle of the
test case that the traces represent?  Or for the entire
duration of the test?  Or none of it at all?  I can't find
any clear evidence of a spike in syscalls/second (to match
what happened on daedalus) anywhere in the trace data.

There's an interesting interval from 1010550089.424071 to
1010550089.550825 when no system calls complete (there are
some reads and at least one stat that run for a long time
during that interval), but the net result of that is a drop
in syscalls/second, not an increase.  Thus I'm not sure if
this is related to the problem, unless the phenomenon on
daedalus happens when a whole lot of syscalls get blocked
for some reason and then all unblock at once.

It looks like you used flood to hit the server with a lot
of requests in parallel, right?.  If so, can you recreate
the problem with a test case that issues just one request
at a time?

>One thing I noticed is that shutdown(2) looks very expensive.
>

 From the traces, the elapsed time for shutdown calls in general appears
to be somewhat smaller than that of open or stat calls.  Are there
specific slow shutdown calls that you're looking at (ones that are
much more expensive than the average)?

--Brian

P.S.: Not one brk call in the entire trace...does that surprise anybody
else?




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