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

From: David Lang
Date: Tue Apr 24 2007 - 03:23:26 EST

On Tue, 24 Apr 2007, Ingo Molnar wrote:

* 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.)

if you are trying to unwedge a system it may be a good idea to renice all tasks to 0, it could be that a task at +19 is holding a lock that something else is waiting for.

David Lang
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