Date: Mon, 06 Sep 2010 15:05:53 -0400 From: jhell <jhell@DataIX.net> To: David Xu <davidxu@freebsd.org> Cc: jan.grant@bristol.ac.uk, freebsd-stable@freebsd.org, Andriy Gapon <avg@icyb.net.ua>, Ivan Voras <ivoras@freebsd.org> Subject: Re: Tuning the scheduler? Desktop with a CPU-intensive task becomes rapidly unusable. Message-ID: <4C853B91.4090601@DataIX.net> In-Reply-To: <4C818F65.3000603@freebsd.org> References: <alpine.BSF.2.00.1009011357050.5858@tribble.ilrt.bris.ac.uk> <i5lr29$9ei$1@dough.gmane.org> <alpine.BSF.2.00.1009021000110.50312@tribble.ilrt.bris.ac.uk> <4C7F7C0F.8080004@icyb.net.ua> <alpine.BSF.2.00.1009021133330.5858@tribble.ilrt.bris.ac.uk> <4C818F65.3000603@freebsd.org>
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On 09/03/2010 20:14, David Xu wrote: > jan.grant@bristol.ac.uk wrote: >> On Thu, 2 Sep 2010, Andriy Gapon wrote: >> >> >>> on 02/09/2010 12:08 jan.grant@bristol.ac.uk said the following: >>> >>>> On Wed, 1 Sep 2010, Ivan Voras wrote: >>>> >>>> >>>>> 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? >>>>> >>>> Not 100%, but mostly convinced; I've just started looking at >>>> this. It's my first stab at what might be going on. X11 >>>> performance is usually pretty snappy. There's no paging >>>> pressure at all. >>>> >>> From my experience: 1. system with Athlon II X2 250 CPU and >>> onboard AMD graphics - no issues with interaction between >>> buildworld and GUI with all KDE4 effects enabled (OpenGL). 2. >>> system with comparable Core2 Duo CPU and onboard Intel graphics >>> (G33) - enabling OpenGL desktop effects in KDE4 leads to the >>> consequences like what you describe. With all GUI bells and >>> whistles disabled the system behaves quite like the AMD system. >>> >> >> All desktop effects are disabled. The graphics are from an nVidia >> GeForce 8500 GT (G86) with the X.org driver. (It's not _just_ >> desktop behaviour that's affected, though: the box runs a number of >> small headless [interactive] server processes which also appear to >> get rapidly starved of CPU time.) >> >> The behaviour isn't visible with the 4bsd scheduler; "stuff" >> generally remains snappy and responsive. >> >> I'll keep poking around and see if I can get to the bottom of it. >> >> >> >> > I think sysctl kern.sched.preempt_thresh is too low, default is only > 64. I always tune it up to 200 on my desktop machine which is > running gnome and other GUI applications, for a heavy GUI deskkop, I > would tune it up to 224 to get better result. > For reference how did you arrive at 224 for a result ? -- jhell,v
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