Re: CFS review

[Bill Davidsen <davidsen@tmr.com>]

Al Boldi wrote:
> Ingo Molnar wrote:
> > * Al Boldi <a1426z@gawab.com> wrote:
> > > > > The problem is that consecutive runs don't give consistent results
> > > > > and sometimes stalls.  You may want to try that.
> > > > well, there's a natural saturation point after a few hundred tasks
> > > > (depending on your CPU's speed), at which point there's no idle time
> > > > left. From that point on things get slower progressively (and the
> > > > ability of the shell to start new ping tasks is impacted as well),
> > > > but that's expected on an overloaded system, isnt it?
> > > Of course, things should get slower with higher load, but it should be
> > > consistent without stalls.
> > >
> > > To see this problem, make sure you boot into /bin/sh with the normal
> > > VGA console (ie. not fb-console).  Then try each loop a few times to
> > > show different behaviour; loops like:
> > >
> > > # for ((i=0; i<3333; i++)); do ping 10.1 -A > /dev/null & done
> > >
> > > # for ((i=0; i<3333; i++)); do nice -99 ping 10.1 -A > /dev/null & done
> > >
> > > # { for ((i=0; i<3333; i++)); do
> > >         ping 10.1 -A > /dev/null &
> > >     done } > /dev/null 2>&1
> > >
> > > Especially the last one sometimes causes a complete console lock-up,
> > > while the other two sometimes stall then surge periodically.
> > ok. I think i might finally have found the bug causing this. Could you
> > try the fix below, does your webserver thread-startup test work any
> > better?
>
> It seems to help somewhat, but the problem is still visible.  Even v20.3 on 
> 2.6.22.5 didn't help.
>
> It does look related to ia-boosting, so I turned off __update_curr like Roman 
> mentioned, which had an enormous smoothing effect, but then nice levels 
> completely break down and lockup the system.
>
> There is another way to show the problem visually under X (vesa-driver), by 
> starting 3 gears simultaneously, which after laying them out side-by-side 
> need some settling time before smoothing out.  Without __update_curr it's 
> absolutely smooth from the start.

I posted a LOT of stuff using the glitch1 script, and finally found a 
set of tuning values which make the test script run smooth. See back 
posts, I don't have them here.

--
Bill Davidsen <davidsen@tmr.com>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/