Re: 2.5.47 scheduler problems?

Mike Galbraith
2002-11-18T10:51:33Z

----- Original Message -----
From: "Tim Connors" <tconnors@astro.swin.edu.au>
To: "Mike Galbraith" <EFAULT@gmx.de>
Cc: <linux-kernel@vger.kernel.org>
Sent: Monday, November 18, 2002 8:53 AM
Subject: Re: 2.5.47 scheduler problems?

> On Mon, 18 Nov 2002, Mike Galbraith wrote:
>
> > > > If I do the same in 2.5.47, I have no control of my box.
Setting
> > all tasks
> > > > to SCHED_FIFO or SCHED_RR prior to starting make -j10 bzImage, I
can
> > regain
> > > > control, but interactivity under load is basically not present.
> > >
> > > Funny that.
> > >
> > > > I used to be able to wave a window poorly at make -j25 (swapping
> > heftily),
> > > > fairly smoothly at make -j20, and smoothly at make -j15 or
below.
> > This
> > > > with no SCHED_RR/SCHED_FIFO. (I haven't done much testing like
this
> > in
> > > > quite a while though)
> > >
> > > Perhaps you should consider buying an extra 29 CPU's for you
desktop?
> >
> > I have neither the need for 30 CPUs, nor the cash to pay for such a
> > beast :)
> >
> > I gather you think my test is silly?
>
> Well, yes, 30 processes at a time on a single CPU does seem a bit
silly -
> given that (under the old system), you would not expect X to get more
than
> 3% of the CPU time.

I don't try -j30 with X/KDE running.. that's much too heavy for my
little box. The whole point of doing -j30 on my box without X/KDE is
that it juuuust fills up capacity. It generally adds a minute to build
time despite quite hefty swapping. With aa kernels or heavily twiddled
stock kernels, it's more like 30 seconds. (with new gcc, -j30 is way
too much too.. oink oink;)

> Also sceduling normal processes (ie, not real-time processes) as
RR/FIFO
> seemed also pretty bad.

That was only to see if I _could_ get some CPU, and with (only:) 10
copies of gcc running.

>
> However....
>
> But I have to now admit that I haven't yet played with 2.5.47
seriously,
> and wansn't aware of the problems which Andrew just posted.
>
> mea culpa.
>
>
> --
> TimC -- http://astronomy.swin.edu.au/staff/tconnors/

-Mike