Date: Tue, 15 Jun 2004 17:16:53 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Daniel Eischen <eischen@vigrid.com> Cc: freebsd-threads@freebsd.org Subject: Re: Possible Threading problem with -CURRENT / MySQL? Message-ID: <Pine.NEB.3.96L.1040615154907.66022E-100000@fledge.watson.org> In-Reply-To: <Pine.GSO.4.10.10406151124360.29429-100000@pcnet5.pcnet.com>
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On Tue, 15 Jun 2004, Daniel Eischen wrote: > > My results were without HTT (It was FreeBSD-AMD64) I didn't have any memory > > options > > or a mysql config file. > > > > _This problem is directly related to a commit that was made between ~May 18 > > and yesterday._ > > There was a subsystem lock(s) put in for networking a few days ago. > There were no changes to the threads library that would exhibit the > behavior you are seeing. The candidate time range includes a number of big and relevant changes: - mbuma becomes the mbuf allocator, which would affect heavy UNIX domain socket I/O since mbufs are used for that I/O on local mysql configurations. Since general benchmarks I've seen suggest mbuma helps or has the same cost as the previous allocator, presumably it would be some special case regression. - Coarse-grained locking was introduced in UNIX domain sockets, but Giant has not yet been removed. This means we're paying an additional (and redundant) locking overhead without the benefits of the finer-grained locking model in the base tree. I've set up a test box to look at the performance impact of that today to see if it resulted in a substantial regression. I'd expect a few percent, but maybe it's worse and it would be good to know. - There have been a number of amd64-related VM changes, optimizations, etc. Maybe one didn't work out so well. I don't have an amd64-box so I can't really reason about that too much just now. If we can track down the date a little closer, that would help a lot. Even just adding a new data point for June 1 or June 7 would be helpful. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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