From mboxrd@z Thu Jan  1 00:00:00 1970
From: Frederic Weisbecker <frederic-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [RFC PATCH 6/6] cpuset: Add cpuset.isolation_mask file
Date: Mon, 19 Jul 2021 15:17:04 +0200
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To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Valentin Schneider <valentin.schneider-5wv7dgnIgG8@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Alex Belits <abelits-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>, Nitesh Lal <nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Nicolas Saenz <nsaenzju-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Christoph Lameter <cl-LoxgEY9JZOazQB+pC5nmwQ@public.gmane.org>, Marcelo Tosatti <mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Zefan Li <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

On Thu, Jul 15, 2021 at 11:04:19AM +0200, Peter Zijlstra wrote:
> On Thu, Jul 15, 2021 at 01:13:38AM +0200, Frederic Weisbecker wrote:
> > On Wed, Jul 14, 2021 at 06:52:43PM +0200, Peter Zijlstra wrote:
> 
> > > cpusets already has means to create paritions; why are you creating
> > > something else?
> > 
> > I was about to answer that the semantics of isolcpus, which reference
> > a NULL domain, are different from SD_LOAD_BALANCE implied by
> > cpuset.sched_load_balance. But then I realize that SD_LOAD_BALANCE has
> > been removed.
> > 
> > How cpuset.sched_load_balance is implemented then? Commit
> > e669ac8ab952df2f07dee1e1efbf40647d6de332 ("sched: Remove checks against
> > SD_LOAD_BALANCE") advertize that setting cpuset.sched_load_balance to 0
> > ends up creating NULL domain but that's not what I get. For example if I
> > mount a single cpuset root (no other cpuset mountpoints):
> 
> SD_LOAD_BALANCE was only for when you wanted to stop balancing inside a
> domain tree. That no longer happens (and hasn't for a *long* time).
> Cpusets simply creates multiple domain trees (or the empty one if its
> just one CPU).

Ok.

> 
> > $ mount -t cgroup none ./cpuset -o cpuset
> > $ cd cpuset
> > $ cat cpuset.cpus
> > 0-7
> > $ cat cpuset.sched_load_balance
> > 1
> > $ echo 0 > cpuset.sched_load_balance
> > $ ls /sys/kernel/debug/domains/cpu1/
> > domain0  domain1
> > 
> > I still get the domains on all CPUs...
> 
> (note, that's the cgroup-v1 interface, the cgroup-v2 interface is
> significantly different)
> 
> I'd suggest doing: echo 1 > /debug/sched/verbose, if I do the above I
> get:
> 
> [1290784.889705] CPU0 attaching NULL sched-domain.
> [1290784.894830] CPU1 attaching NULL sched-domain.

Thanks!

Eventually I uninstalled cgmanager and things seem to work now. I have
no idea why and I'm not sure I'm willing to investigate further :o)