Re: [PATCH][RSDL-mm 0/7] RSDL cpu scheduler for 2.6.21-rc3-mm2

Ingo Molnar
2007-03-13T08:09:20Z

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> > It has been said that "perfection is the enemy of good". The two
> > interactive tasks receiving 40% cpu while two niced background jobs
> > receive 60% may well be perfect, but it's damn sure not good.
>
> Well, the real problem is really "server that works on behalf of
> somebody else".

i think Mike's testcase was even simpler than that: two plain CPU hogs
on nice +5 stole much more CPU time with Con's new interactivity code
than they did with the current interactivity code. I'd agree with Mike
that a phenomenon like that needs to be fixed.

/less/ interactivity we can do easily in the current scheduler: just
remove various bits here and there. The RSDL promise is that it gives us
/more/ interactivity (with 'interactivity designed in', etc.), which in
Mike's testcase does not seem to be the case.

> And the problem is that a lot of clients actually end up doing *more*
> in the X server than they do themselves directly.

yeah. It's a hard case because X is not always a _clear_ interactive
task - still the current interactivity code handles it quite well.

but Mike's scenario wasnt even that complex. It wasnt even a hard case
of X being starved by _other_ interactive tasks running on the same nice
level. Mike's test-scenario was about two plain nice +5 CPU hogs
starving nice +0 interactive tasks more than the current scheduler does,
and this is really not an area where we want to see any regression. Con,
could you work on this area a bit more?

Ingo