Date: Wed, 01 Sep 2010 17:21:47 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-stable@freebsd.org Subject: Re: Tuning the scheduler? Desktop with a CPU-intensive task becomes rapidly unusable. Message-ID: <i5lr29$9ei$1@dough.gmane.org> In-Reply-To: <alpine.BSF.2.00.1009011357050.5858@tribble.ilrt.bris.ac.uk> References: <alpine.BSF.2.00.1009011357050.5858@tribble.ilrt.bris.ac.uk>
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On 09/01/10 15:08, jan.grant@bristol.ac.uk wrote: > I'm running -STABLE with a kde-derived desktop. This setup (which is > pretty standard) is providing abysmal interactive performance on an > eight-core machine whenever I try to do anything CPU-intensive (such as > building a port). > > Basically, trying to build anything from ports rapidly renders everything > else so "non-interactive" in the eyes of the scheduler that, for instance, > switching between virtual desktops (I have six of them in reasonably > frequent use) takes about a minute of painful waiting on redraws to > complete. Are you sure this is about the scheduler or maybe bad X11 drivers? > Once I pay attention to any particular window, the scheduler rapidly > (like, in 15 agonising seconds or so) decides that the processes > associated with that particular window are "interactive" and performance > there picks up again. But it only takes 10 seconds (not timed; ballpark > figures) or so of inattention for a window's processes to lapse back into > a low-priority state, with the attendant performance problems. "windows" in X11 have nothing to do with the scheduler (contrary to MS Windows where the OS actually "re-nices" processes whose windows have focus) - here you are just interacting with a process. > I don't think my desktop usage is particularly abnormal; I doubt my level > of frustration is, either :-) I think the issue here is that a modern I'm writing this on a quad-core Core2 machine with 4 GB RAM, amd64 arch, Radeon 2500 HD, with KDE4 with most of the 3D visual effects turned on. I have not yet experienced problems like you describe. On the other hand, I have noticed that a 2xQuad-core machine I have access too has more X11 interactivity problems than this single quad-core machine, though again not as serious as yours. I don't know why this is. From the hardware side it might be the shared FSB or from the software side it might be the scheduler. If you want to try something I think it's easier for you to disable one CPU in BIOS or pin X.org and its descendant processes to CPUs of a single socket than to diagnose scheduler problems. > but compared to the performance under sched_4bsd, what I'm seeing is an > atrocious user experience. It would be best if you could quantify this in some way. I have no idea how.
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