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From: Frederic Weisbecker <frederic@kernel.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Alex Belits <abelits@marvell.com>, Nitesh Lal <nilal@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nicolas Saenz <nsaenzju@redhat.com>,
	Christoph Lameter <cl@gentwo.de>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Zefan Li <lizefan.x@bytedance.com>,
	cgroups@vger.kernel.org
Subject: Re: [RFC PATCH 6/6] cpuset: Add cpuset.isolation_mask file
Date: Thu, 15 Jul 2021 02:07:06 +0200	[thread overview]
Message-ID: <20210715000706.GA75036@lothringen> (raw)
In-Reply-To: <87o8b4mpfb.mognet@arm.com>

On Thu, Jul 15, 2021 at 12:44:08AM +0100, Valentin Schneider wrote:
> On 15/07/21 01:13, 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):
> >
> > $ 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...
> 
> Huh. That's on v5.14-rc1 with an automounted cpuset:
> 
> $ cat /sys/fs/cgroup/cpuset/cpuset.cpus
> 0-5
> $ cat /sys/fs/cgroup/cpuset/cpuset.sched_load_balance
> 1
> 
> $ ls /sys/kernel/debug/sched/domains/cpu*
> /sys/kernel/debug/sched/domains/cpu0:
> domain0  domain1
> 
> /sys/kernel/debug/sched/domains/cpu1:
> domain0  domain1
> 
> /sys/kernel/debug/sched/domains/cpu2:
> domain0  domain1
> 
> /sys/kernel/debug/sched/domains/cpu3:
> domain0  domain1
> 
> /sys/kernel/debug/sched/domains/cpu4:
> domain0  domain1
> 
> /sys/kernel/debug/sched/domains/cpu5:
> domain0  domain1
> 
> $ echo 0 > /sys/fs/cgroup/cpuset/cpuset.sched_load_balance
> $ ls /sys/kernel/debug/sched/domains/cpu*
> /sys/kernel/debug/sched/domains/cpu0:
> 
> /sys/kernel/debug/sched/domains/cpu1:
> 
> /sys/kernel/debug/sched/domains/cpu2:
> 
> /sys/kernel/debug/sched/domains/cpu3:
> 
> /sys/kernel/debug/sched/domains/cpu4:
> 
> /sys/kernel/debug/sched/domains/cpu5:
> 
> 
> I also checked that you can keep cpuset.sched_load_balance=0 at the root
> and create exclusive child cpusets with different values of
> sched_load_balance, giving you some CPUs attached to the NULL domain and
> some others with a sched_domain hierarchy that stays within the cpuset span.

Ok I must have done something wrong somewhere, I'll check further tomorrow.

Thanks!

  reply	other threads:[~2021-07-15  0:07 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14 13:54 [RFC PATCH 0/6] cpuset: Allow to modify isolcpus through cpuset Frederic Weisbecker
2021-07-14 13:54 ` [RFC PATCH 1/6] pci: Decouple HK_FLAG_WQ and HK_FLAG_DOMAIN cpumask fetch Frederic Weisbecker
2021-07-14 13:54 ` [RFC PATCH 2/6] workqueue: " Frederic Weisbecker
2021-07-14 13:54 ` [RFC PATCH 3/6] net: " Frederic Weisbecker
2021-07-14 13:54 ` [RFC PATCH 4/6] sched/isolation: Split domain housekeeping mask from the rest Frederic Weisbecker
2021-07-14 13:54 ` [RFC PATCH 5/6] sched/isolation: Make HK_FLAG_DOMAIN mutable Frederic Weisbecker
2021-07-21 14:28   ` Vincent Donnefort
2021-07-14 13:54 ` [RFC PATCH 6/6] cpuset: Add cpuset.isolation_mask file Frederic Weisbecker
2021-07-14 16:31   ` Marcelo Tosatti
2021-07-19 13:26     ` Frederic Weisbecker
2021-07-19 15:41       ` Marcelo Tosatti
2021-07-14 16:52   ` Peter Zijlstra
2021-07-14 23:13     ` Frederic Weisbecker
2021-07-14 23:44       ` Valentin Schneider
2021-07-15  0:07         ` Frederic Weisbecker [this message]
2021-07-15  9:04       ` Peter Zijlstra
2021-07-19 13:17         ` Frederic Weisbecker
2021-07-16 18:02 ` [RFC PATCH 0/6] cpuset: Allow to modify isolcpus through cpuset Waiman Long
2021-07-19 13:57   ` Frederic Weisbecker

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