Re: [REPORT] cfs-v4 vs sd-0.44

From: Ingo Molnar
Date: Tue Apr 24 2007 - 03:09:26 EST

* Gene Heskett <gene.heskett@xxxxxxxxx> wrote:

> > Gene has done some testing under CFS with X reniced to +10 and the
> > desktop still worked smoothly for him.
> As a data point here, and probably nothing to do with X, but I did
> manage to lock it up, solid, reset button time tonight, by wanting
> 'smart' to get done with an update session after amanda had started.
> I took both smart processes I could see in htop all the way to -19,
> but when it was about done about 3 minutes later, everything came to
> an instant, frozen, reset button required lockup. I should have
> stopped at -17 I guess. :(

yeah, i guess this has little to do with X. I think in your scenario it
might have been smarter to either stop, or to renice the workloads that
took away CPU power from others to _positive_ nice levels. Negative nice
levels can indeed be dangerous.

(Btw., to protect against such mishaps in the future i have changed the
SysRq-N [SysRq-Nice] implementation in my tree to not only change
real-time tasks to SCHED_OTHER, but to also renice negative nice levels
back to 0 - this will show up in -v6. That way you'd only have had to
hit SysRq-N to get the system out of the wedge.)

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