Re: [PATCH v9 3/8] cpuset: Rebuild root domain deadline accounting information

Qais Yousef
2023-01-15T16:41:48Z

On 12/20/22 11:43, Qais Yousef wrote:
> On 12/19/22 09:07, Vincent Guittot wrote:
> > On Sat, 17 Dec 2022 at 00:35, Qais Yousef <qyousef-wp2msK0BRk8tq7phqP6ubQ@public.gmane.org> wrote:
> > >
> > > Hi
> > >
> > > On 07/19/19 15:59, Juri Lelli wrote:
> > > > When the topology of root domains is modified by CPUset or CPUhotplug
> > > > operations information about the current deadline bandwidth held in the
> > > > root domain is lost.
> > > >
> > > > This patch addresses the issue by recalculating the lost deadline
> > > > bandwidth information by circling through the deadline tasks held in
> > > > CPUsets and adding their current load to the root domain they are
> > > > associated with.
> > > >
> > > > Signed-off-by: Mathieu Poirier <mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > > > Signed-off-by: Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > > > ---
> > >
> > > We see that rebuild_root_domain() can take 10+ ms (I get a max of 20ms quite
> > > consistently) on suspend/resume.
> > >
> > > Do we actually need to rebuild_root_domain() if we're going through
> > > a suspend/resume cycle?
> >
> > During suspend to ram, there are cpus hotplug operation but If you use
> > suspend to idle, you will skip cpus hotplug operation and its
> > associated rebuild.
>
> Thanks Vincent. I'll check on that - but if we want to keep suspend to ram?
> Do we really to incur this hit?

Using s2idle is not an option actually. I'll prepare v2 to address Waiman
comment if I don't get more feedback in the next few days.

Thanks!