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

Jim Bryant kc5vdj.freebsd at gmail.com
Fri Sep 3 19:30:23 UTC 2010

i just noticed this too...  had a build going of qt-creator, and then 
started a /usr/src make clean, and had to abort the qt-creator build to 
get the make clean to finish.  it was taking forever to even paint the 
xterm in the make clean window.

-stable built as of last week, amd64 kernel, core2 duo e8200, 4G ram 
(3.9G usable), intel dq45ek motherboard, kde4, compositing turned off.

Luca Pizzamiglio wrote:
> Hello,
> 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).
> Cheers,
> Luca
> 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.

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