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SubjectRe: Bad interactive behaviour in 2.5.65-66 (sched.c)
At 08:35 AM 3/31/2003 +0200, Jens Axboe wrote:
>On Mon, Mar 31 2003, Mike Galbraith wrote:
> > At 07:06 AM 3/31/2003 +1000, Con Kolivas wrote:
> > >On Mon, 31 Mar 2003 00:14, Jens Axboe wrote:
> > >> On Sat, Mar 29 2003, Robert Love wrote:
> > >> > On Sat, 2003-03-29 at 21:33, Con Kolivas wrote:
> > >> > > Are you sure this should be called a bug? Basically X is an
> > >interactive
> > >> > > process. If it now is "interactive for a priority -10 process" then
> > >it
> > >> > > should be hogging the cpu time no? The priority -10 was a workaround
> > >> > > for lack of interactivity estimation on the old scheduler.
> > >> >
> > >> > Well, I do not necessarily think that renicing X is the problem. Just
> > >> > an idea.
> > >>
> > >> I see the exact same behaviour here (systems appears fine, cpu intensive
> > >> app running, attempting to start anything _new_ stalls for ages), and I
> > >> definitely don't play X renice tricks.
> > >>
> > >> It basically made 2.5 unusable here, waiting minutes for an ls to even
> > >> start displaying _anything_ is totally unacceptable.
> > >
> > >I guess I should have trusted my own benchmark that was showing this was
> > >worse
> > >for system responsiveness.
> >
> > I don't think it's really bad for system responsiveness. I think the
>
>What drugs are you on? 2.5.65/66 is the worst interactive kernel I've
>ever used, it would be _embarassing_ to release a 2.6-test with such a
>rudimentary flaw in it. IOW, a big show stopper.

Hehehe... try the attached if you're brave. It took me a loooong time to
get backboost to work right. Mainly because backboost wasn't really broken
:))) This patch _needs_ backboost to work, (see sleep_avg_tick()) and it
does seem to do the job very nicely.
> > problem is just that the sample is too small. The proof is that simply
> > doing sleep_time %= HZ cures most of my woes. WRT contest and it's

The real problem is that there is no information in the fact that you were
in lala land for a year or so. Just because you slept through lunch,
there's nothing that says you'll be a good mood afterward. The useful
information is the fact that someone else got a chance at the cpu, and
you're only a really nice guy if you share a lot. Take a look at what I
did to activate_task()... if you slept for a short time, use that
information. If you slept for a long time, you get exactly what you need
to finish your time slice. This isn't subject to the number of tasks
queued up, so the mistakes are smaller. I also dispose of mistakes faster
to make sure that interactive tasks (which aren't once they start running a
lot) don't eat ages of cpu. With this patch, I can get more than one task
from a make -j30 bzImage in an ext3 partition to run concurrently, _and_ X
is wonderful as well (gee, I really can have my cake and eat it too:).

> Irk, that sounds like a really ugly bandaid.

Well, it was just tossing the most damaging part of the problem into the
bit bucket.

Anyway, anyone who thinks the scheduler is still unfair, or el-sucko in any
way should feel free to beat upon this experiment. I really like this
one... think I'll even keep my fingers off it for a few minutes ;-)

-Mike

Yeah, some of it _is_ gratuitous, but heck, it's almost pure research. (no
kaBoOMs... yet) [unhandled content-type:application/octet-stream]
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