Re: 4.2.2: NR_CPUS effectively being 1 bug

[Frederic Weisbecker]

On Sat, Oct 03, 2015 at 02:04:44PM +0200, Mike Galbraith wrote:
> On Sat, 2015-10-03 at 10:52 +0200, Ingo Molnar wrote:
> > Ok, looks like a patch with good intentions but bad effects. Mind sending a revert 
> > patch, changelogged, signed off?
> 
> No.  They know.

The reason for this patch is that NO_HZ_FULL is only useful on a CPU if no task
other than the desired one can be scheduled on it. Hence the cpu_isolated_map.

Only those who enable NO_HZ_FULL_ALL by accident do complain, not those who
really use it so far. At least it makes people realize their mistake.

That said I never liked that cpu_isolated_map. And some regular non-isolation
work may be needed to be done even on NO_HZ_FULL_ALL machines and it that
case we get screwed.

So I should revert that and defer that isolation work to explicit affinity
setting or cpusets.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/