From: "Michal Koutný" <mkoutny@suse.com>
To: Waiman Long <longman@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shuah Khan <shuah@kernel.org>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH v2 3/4] cgroup/cpuset: Include offline CPUs when tasks' cpumasks in top_cpuset are updated
Date: Fri, 17 Mar 2023 19:01:57 +0100 [thread overview]
Message-ID: <20230317180157.uqlleobldg53pgj6@blackpad> (raw)
In-Reply-To: <20230317151508.1225282-4-longman@redhat.com>
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Hello.
On Fri, Mar 17, 2023 at 11:15:07AM -0400, Waiman Long <longman@redhat.com> wrote:
> * Iterate through each task of @cs updating its cpus_allowed to the
> * effective cpuset's. As this function is called with cpuset_rwsem held,
> - * cpuset membership stays stable.
> + * cpuset membership stays stable. For top_cpuset, task_cpu_possible_mask()
> + * is used instead of effective_cpus to make sure all offline CPUs are also
> + * included as hotplug code won't update cpumasks for tasks in top_cpuset.
> */
On Wed, Mar 15, 2023 at 11:06:20AM +0100, Michal Koutný <mkoutny@suse.com> wrote:
> I see now that it returns offlined cpus to top cpuset's tasks.
I considered only the "base" set change cs->effective_cpus ->
possible_mask. (Apologies for that mistake.)
However, I now read the note about subparts_cpus
> * effective_cpus contains only onlined CPUs, but subparts_cpus
> * may have offlined ones.
So if subpart_cpus keeps offlined CPUs, they will be subtracted from
possible_mask and absent in the resulting new_cpus, i.e. undesirable for
the tasks in that cpuset :-/
Michal
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WARNING: multiple messages have this Message-ID (diff)
From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>
To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Zefan Li <lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>,
Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Shuah Khan <shuah-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kselftest-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Will Deacon <will-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v2 3/4] cgroup/cpuset: Include offline CPUs when tasks' cpumasks in top_cpuset are updated
Date: Fri, 17 Mar 2023 19:01:57 +0100 [thread overview]
Message-ID: <20230317180157.uqlleobldg53pgj6@blackpad> (raw)
In-Reply-To: <20230317151508.1225282-4-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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Hello.
On Fri, Mar 17, 2023 at 11:15:07AM -0400, Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> * Iterate through each task of @cs updating its cpus_allowed to the
> * effective cpuset's. As this function is called with cpuset_rwsem held,
> - * cpuset membership stays stable.
> + * cpuset membership stays stable. For top_cpuset, task_cpu_possible_mask()
> + * is used instead of effective_cpus to make sure all offline CPUs are also
> + * included as hotplug code won't update cpumasks for tasks in top_cpuset.
> */
On Wed, Mar 15, 2023 at 11:06:20AM +0100, Michal Koutný <mkoutny-IBi9RG/b67k@public.gmane.org> wrote:
> I see now that it returns offlined cpus to top cpuset's tasks.
I considered only the "base" set change cs->effective_cpus ->
possible_mask. (Apologies for that mistake.)
However, I now read the note about subparts_cpus
> * effective_cpus contains only onlined CPUs, but subparts_cpus
> * may have offlined ones.
So if subpart_cpus keeps offlined CPUs, they will be subtracted from
possible_mask and absent in the resulting new_cpus, i.e. undesirable for
the tasks in that cpuset :-/
Michal
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next prev parent reply other threads:[~2023-03-17 18:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-17 15:15 [PATCH v2 0/4] cgroup/cpuset: Miscellaneous updates Waiman Long
2023-03-17 15:15 ` Waiman Long
2023-03-17 15:15 ` [PATCH v2 1/4] cgroup/cpuset: Fix partition root's cpuset.cpus update bug Waiman Long
2023-03-29 18:37 ` Tejun Heo
2023-03-29 18:37 ` Tejun Heo
2023-03-17 15:15 ` [PATCH v2 2/4] cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset Waiman Long
2023-03-17 15:15 ` Waiman Long
2023-03-17 15:15 ` [PATCH v2 3/4] cgroup/cpuset: Include offline CPUs when tasks' cpumasks in top_cpuset are updated Waiman Long
2023-03-17 18:01 ` Michal Koutný [this message]
2023-03-17 18:01 ` Michal Koutný
2023-03-17 18:05 ` Waiman Long
2023-03-17 18:05 ` Waiman Long
2023-03-20 15:04 ` Michal Koutný
2023-03-20 15:04 ` Michal Koutný
2023-03-17 15:15 ` [PATCH v2 4/4] cgroup/cpuset: Minor updates to test_cpuset_prs.sh Waiman Long
2023-03-17 15:15 ` Waiman Long
2023-03-29 18:43 ` Tejun Heo
2023-03-28 13:40 ` [PATCH v2 0/4] cgroup/cpuset: Miscellaneous updates Will Deacon
2023-03-28 13:40 ` Will Deacon
2023-03-29 1:15 ` Waiman Long
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