Re: [patch] CFS scheduler, -v8

Ingo Molnar
2007-05-02T10:41:22Z

* Mike Galbraith <efault@gmx.de> wrote:

> On Tue, 2007-05-01 at 23:22 +0200, Ingo Molnar wrote:
> > - interactivity: precise load calculation and load smoothing
>
> This seems to help quite a bit.

great :)

> (5 second top sample)
>
> 2636 root 15 -5 19148 15m 5324 R 73 1.5 1:42.29 0 amarok_libvisua
> 5440 root 20 0 320m 36m 8388 S 18 3.6 3:28.55 1 Xorg
> 4621 root 20 0 22776 18m 4168 R 12 1.8 0:00.63 1 cc1
> 4616 root 20 0 19456 13m 2200 R 9 1.3 0:00.43 0 cc1
>
> I no longer have to renice both X and Gforce to achieve a perfect
> display when they are sharing my box with a make -j2. X is displaying
> everything it's being fed beautifully with no help. I have to renice
> Gforce (amarok_libvisual), but given it's very heavy CPU usage, that
> seems perfectly fine.

ah! Besides OpenGL behavior and app startup performance i didnt
originally have Xorg in mind with this change, but thinking about it,
precise load calculations and load smoothing does have a positive effect
on 'coupled' workloads where under the previous variant of CFS's load
calculation one task component of the workload could become 'invisible'
to another task and hence cause macro-scale scheduling artifacts not
expected by humans. With smoothing these are dealt with more
consistently. Xorg can be a quite strongly coupled workload.

> No regressions noticed so far. Box is _very_ responsive under load,
> seemingly even more so than with previous releases. That is purely
> subjective, but the first impression was very distinct.

yeah, make -jN workloads (and any mixture of non-identical scheduling
patterns, which most real workloads consist of) should be handled more
consistently too by -v8.

so your workload (and Gene's workload) were the ones in fact that i had
hoped not to _hurt_ with -v8 (neither of you being the hardcore gamer
type ;), and in reality -v8 ended up helping them too. These sorts of
side-effects are always welcome ;-)

Ingo