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From Greg Ames <>
Subject Re: load spikes revisited
Date Fri, 18 Jan 2002 00:52:41 GMT
Greg Ames wrote:    

>       While trying out ktrace on my test config, I saw that
> the fcntl() accept mutex has got a thundering herd problem on daedalus.  

uhhh, I might have been wrong about this.  

Looking at the ktrace from 2.0.30-dev in production last night, I see very
similar behavior (big bunches of processes getting woken up and immediately
going back to sleep with no intervening trace records) for processes that are
blocked in select or poll with a timeout.  This happens maybe 8-16 times a
second until the timeout expires or the socket is ready.  

If one of those timers popped at about the same time the fcntl mutex was
released, it would look pretty much the same as what I saw with the test
config.  So let's look at FreeBSD's fcntl locking more closely before we rip it
out.  I sure wish there was a timer interrupt trace record.


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