Date: Sat, 04 Sep 2010 08:14:29 +0800 From: David Xu <davidxu@freebsd.org> To: jan.grant@bristol.ac.uk Cc: 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: <4C818F65.3000603@freebsd.org> In-Reply-To: <alpine.BSF.2.00.1009021133330.5858@tribble.ilrt.bris.ac.uk> 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>
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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. Regards, David Xu
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