Re: + kmod-remove-unecessary-explicit-wide-cpu-affinity-setting.patch added to -mm tree

From: Frederic Weisbecker
Date: Wed Jul 08 2015 - 08:52:22 EST


On Wed, Jul 08, 2015 at 01:32:26AM +0200, Oleg Nesterov wrote:
> Well, sorry for noise.
>
> Let me repeat that I agree with this change, but...
>
> On 07/07, Andrew Morton wrote:
> >
> > From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > Subject: kmod: remove unecessary explicit wide CPU affinity setting
> >
> > Not only useless it even breaks nohz full. The housekeeping work (general
> > kernel internal code that user doesn't care much about) is handled by a
> > reduced set of CPUs in nohz full, precisely those that are not included by
> > nohz_full= kernel parameters. For example unbound workqueues are handled
> > by housekeeping CPUs.
>
> I still think this part of the changelog looks confusing and just wrong.

I agree!

>
> It is not that it breaks nohz full, unbound workqueues have nothing to
> do with housekeeping_mask from the kernel pov. But yes, people can change
> ->cpumask and this can connect to housekeeping_mask.

Right. In fact that's the motivation of the patch but the connection is
much more indirect than what the changelog suggests. So I'll fix the changelog.

>
> Frederic, may I ask you to update the changelog? Although perhaps it was
> just me who was confused...

Sure! I think Andrew applied the patches to keep track of them and make sure
they don't get lost. But I'm working on a new iteration to replace them.

Thanks!

> Oleg.
>
--
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/