Tuning the scheduler? Desktop with a CPU-intensive task becomes rapidly unusable.

Luca Pizzamiglio l.pizzamiglio at bally-wulff.de
Thu Sep 2 13:07:21 UTC 2010


My machine has a similar behavior. For instance, during intensive 
workload (portupgrade), everything is quite not-responsive.

I made an alias of portupgrade, nice -n 5 portupgrade, that solves the 
problem just in that particular case.

My system is AMD Athlon(tm) 64 Processor 3000+ (1809.28-MHz 686-class 
CPU) with openGL effects disabled, KDE as desktop environment.

There is an interesting mib kern.sched.interact. But I don't know the 
meaning of it (my value is 30).


On 09/02/2010 12:46, jan.grant at bristol.ac.uk wrote:
> On Thu, 2 Sep 2010, Andriy Gapon wrote:
>> on 02/09/2010 12:08 jan.grant at bristol.ac.uk said the following:
>>> On Wed, 1 Sep 2010, Ivan Voras wrote:
>>>> On 09/01/10 15:08, jan.grant at 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.

Mit herzlichen Grüßen,

Luca Pizzamiglio

BALLY WULFF Entertainment GmbH
Maybachufer 48-51
12045 Berlin
Phone:  +49(30)62002 149

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