Date: Wed, 19 Nov 2003 10:02:01 -0500 (EST) From: Robert Watson <rwatson@freebsd.org> To: matthew tillman <maffew@sbcglobal.net> Cc: freebsd-smp@freebsd.org Subject: Re: device pcm kills SMP performance -CURRENT Message-ID: <Pine.NEB.3.96L.1031119100015.7131D-100000@fledge.watson.org> In-Reply-To: <20031112210917.10741.qmail@web80103.mail.yahoo.com>
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On Wed, 12 Nov 2003, matthew tillman wrote: > I have an ACorp 6A815EPD motherboard, Intel i815 chipset, with a pair of > P3 733s. My sound card, is a SoundBlaster Live Value. > > Whenever sound support is compiled in the Kernel, performance takes a > huge hit, X runs about the same as on a P2 300 or so. But If I boot to a > kernel that is configured exactly the same, without device pcm, the > system is very responsive. > > Booting to a non-SMP kernel in 5.1-Release with or without sound > support, the system was very fast. I did not try no sound support with > SMP, as I thought the issue was only SMP performance in general. > > I then CVSuped to -CURRENT on Nov 8th, because at the time I didn't > realise the issue was isolated to the sound system. However, I still > have the same issue. > > I also tried swapping the card into a diffrent PCI slot, but that didn't > help. Just to confirm -- when you upgraded to -CURRENT, did you remove INVARIANTS and WITNESS from your kernel configuration? They both add substantial overhead to locking operations, and while invaluable to debugging, they can have quite a detrimental affect on performance (see also UPDATING: Why Is Current Slow?). 5.1-RELEASE has these features disabled by default, but 5.1-CURRENT has them enabled since there's active locking work going on. There's also a set of patches being floated to improve pcm locking in a variety of ways, but I'm not sure what the status of those patches is. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Network Associates Laboratories
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