Re: SCHED_ULE on desktop system

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.

Kris