Date: Sun, 13 Jul 2008 03:11:23 +0200 From: Kris Kennaway <kris@FreeBSD.org> To: Nate Eldredge <neldredge@math.ucsd.edu> Cc: freebsd-hackers@freebsd.org Subject: Re: SCHED_4BSD bad interactivity on 7.0 vs 6.3 Message-ID: <4879563B.5090201@FreeBSD.org> In-Reply-To: <Pine.GSO.4.64.0807121125300.20326@zeno.ucsd.edu> References: <Pine.GSO.4.64.0807121125300.20326@zeno.ucsd.edu>
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Nate Eldredge wrote: > Hi folks, > > Hopefully this is a good list for this topic. > > It seems like there has been a regression in interactivity from > 6.3-RELEASE to 7.0-RELEASE when using the SCHED_4BSD scheduler. After > upgrading my single-cpu amd64 box, 7.0 has much worse latency. When > running a kernel compile, there is a noticeable lag to echo my typing or > scroll my browser windows, and playing an mp3 frequently cuts out for a > second or two. This did not happen on 6.3-RELEASE. Are you sure it's not the x.org server bug that was present in the version shipped with 7.0? Update to the latest version and see if your X interactivity improves. Kris > I wrote a small program which forks two processes that run > gettimeofday() in a tight loop to see how long they get scheduled out. > On 6.3 the maximum latency is usually under 100 ms. On 7.0 it is 500 ms > or more even when nothing else is running on the system. When a compile > is also running it is sometimes 1400 ms or more. > > SCHED_ULE is much better, so I've switched over. But it's not the > default yet, and most people are still going to be using SCHED_4BSD. It > used to be acceptable but now it isn't. Does anyone know why it's > regressed so badly? >
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