SCHED_ULE on desktop system
Ganbold
ganbold at micom.mng.net
Tue Sep 18 19:06:24 PDT 2007
Jeff Roberson wrote:
>
> On Mon, 17 Sep 2007, Ganbold wrote:
>
>> Jeff Roberson wrote:
>>> On Mon, 17 Sep 2007, Kris Kennaway wrote:
>>>
>>>> Kevin Oberman wrote:
>>>>>> Date: Sun, 16 Sep 2007 14:47:54 -0700
>>>>>> From: "David E. Thiel" <lx at FreeBSD.org>
>>>>>> Sender: owner-freebsd-current at freebsd.org
>>>>>>
>>>>>> On Sun, Sep 16, 2007 at 12:58:33AM -0700, vehemens wrote:
>>>>>>> On Saturday 15 September 2007 11:19:32 pm Roman Bogorodskiy wrote:
>>>>>>>> I'm curious if SCHED_ULE is designed to be used on a desktop
>>>>>>>> system. I'm
>>>>>>>> running -CURRENT at home and tried to use SCHED_ULE for some
>>>>>>>> time. It
>>>>>>>> works alright while the load is not very high. But once I start
>>>>>>>> compiling something (running 'make buildworld' or 'portupgrade
>>>>>>>> -a' for
>>>>>>>> example), the machine comes almost unusable - X11's windows
>>>>>>>> takes a lot
>>>>>>>> of time to redraw, changing virtual desktop in window manager
>>>>>>>> may take
>>>>>>>> a several seconds. And it's nearly impossible to watch some
>>>>>>>> movie with
>>>>>>>> mplayer.
>>>>>>> I also see something similar running -CURRENT with SCHED_4BSD,
>>>>>>> but it shows up with X/gnome. Remote logins are still responsive
>>>>>>> and running X/twm works fine.
>>>>>> In my experience, both 4BSD and ULE are unresponsive on the desktop
>>>>>> in -CURRENT, with ULE being somewhat worse. Compiling an application
>>>>>> causes the mouse to be jerky, windows to draw slowly, audio to start
>>>>>> skipping, and occasionally the whole desktop freezes for a minute at
>>>>>> a time (with ULE only). This is with INVARIANTS and all the
>>>>>> debugging
>>>>>> kernel options disabled and malloc debugging turned off. I'll
>>>>>> give running without PREEMPTION with 4BSD and the ULE patch a shot,
>>>>>> but in its stock form, -CURRENT is definitely worse than -STABLE
>>>>>> on the
>>>>>> desktop for me in a UP configuration. Up till now, I've been working
>>>>>> around it manually by juggling with rtprio.
>>>>>>
>>>>>> If it's of any use, dmesg is at:
>>>>>>
>>>>>> http://redundancy.redundancy.org/dmesg.txt
>>>>>
>>>>> I have been seeing this for quite some time and, while the
>>>>> scheduler may
>>>>> make a bit of difference, I suspect pager issues. As long as I have
>>>>> available memory, interactivity is fine. If I run a big build and
>>>>> I see
>>>>> swap file use, things slow to a crawl. I see very slow re-draws of
>>>>> the
>>>>> screen and general lack of responsiveness.
>>>>>
>>>>> I run gkrellm and can tell at a glance when swap usage starts to
>>>>> increase. The linkage is clear and not terribly surprising. It may be
>>>>> that you need to add a bit more RAM.
>>>>
>>>> Yes, not surprising in the least. When your system touches swap,
>>>> performance will drop to a tiny fraction of its normal performance.
>>>> Depending on your disk this could be 1% or lower. Anyone who is
>>>> seeing poor interactive performance needs to rule this out as the
>>>> cause.
>>>
>>> Ah, I think I know why people are reporting worse problems with
>>> ULE. ULE is not properly accounting swtime so different threads are
>>> being chosen for swapout with ULE and 4BSD. My test systems all
>>> have more than enough memory to do parallel buildworlds without
>>> swapping. This is likely why I haven't run into this.
>>>
>>> I really need to fix p_swtime with ULE. Could the people reporting
>>> bad behavior please verify whether or not you're seeing swapping
>>> activity? Even just looking for swap used in top will help me verify
>>> that this is the problem.
>>
>> I explained my problem in
>> http://lists.freebsd.org/pipermail/freebsd-current/2007-August/076450.html.
>>
>> This is a UP system and I have 1GB RAM and top results are shown
>> there.
>
> Ganbold,
>
> Thank you for your report. I just sent a follow-up mail to current
> with a patch that addresses this issue. Can you test and report back?
Sorry Jeff, I'm away from office and probably can't test this patch
until beginning of October :(
But as long as I get a chance I will test it.
thanks a lot,
Ganbold
>
> Thanks!
> Jeff
>
>>
>>
>> Ganbold
>>
>>>
>>> Thanks,
>>> Jeff
>>>
>>>
>>>>
>>>> Kris
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>>
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