From: Felix Moessbauer <felix.moessbauer@siemens.com>
To: longman@redhat.com
Cc: akpm@linux-foundation.org, cgroups@vger.kernel.org,
corbet@lwn.net, frederic@kernel.org, guro@fb.com,
hannes@cmpxchg.org, juri.lelli@redhat.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, lizefan.x@bytedance.com,
mkoutny@suse.com, mtosatti@redhat.com, pauld@redhat.com,
peterz@infradead.org, shuah@kernel.org, tj@kernel.org,
jan.kiszka@siemens.com, henning.schild@siemens.com
Subject: Re: [PATCH v8 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus
Date: Wed, 10 Nov 2021 12:13:57 +0100 [thread overview]
Message-ID: <20211110111357.17617-1-felix.moessbauer@siemens.com> (raw)
In-Reply-To: <20211018143619.205065-1-longman@redhat.com>
Hi Weiman,
> v8:
> - Reorganize the patch series and rationalize the features and
> constraints of a partition.
> - Update patch descriptions and documentation accordingly.
>
> v7:
> - Simplify the documentation patch (patch 5) as suggested by Tejun.
> - Fix a typo in patch 2 and improper commit log in patch 3.
>
> v6:
> - Remove duplicated tmpmask from update_prstate() which should fix the
> frame size too large problem reported by kernel test robot.
>
> This patchset makes four enhancements to the cpuset v2 code.
>
> Patch 1: Enable partition with no task to have empty cpuset.cpus.effective.
>
> Patch 2: Refining the features and constraints of a cpuset partition
> clarifying what changes are allowed.
>
> Patch 3: Add a new partition state "isolated" to create a partition
> root without load balancing. This is for handling intermitten workloads
> that have a strict low latency requirement.
I just tested this patch-series and can confirm that it works on 5.15.0-rc7-rt15 (PREEMT_RT).
However, I was not able to see any latency improvements when using
cpuset.cpus.partition=isolated.
The test was performed with jitterdebugger on CPUs 1-3 and the following cmdline:
rcu_nocbs=1-4 nohz_full=1-4 irqaffinity=0,5-6,11 intel_pstate=disable
On the other cpus, stress-ng was executed to generate load.
Just some more general notes:
Even with this new "isolated" type, it is still very tricky to get a similar
behavior as with isolcpus (as long as I don't miss something here):
Consider an RT application that consists of a non-rt thread that should be floating
and a rt-thread that should be placed in the isolated domain.
This requires cgroup.type=threaded on both cgroups and changes to the application
(threads have to be born in non-rt group and moved to rt-group).
Theoretically, this could be done externally, but in case the application sets the
affinity mask manually, you run into a timing issue (setting affinities to CPUs
outside the current cpuset.cpus results in EINVAL).
Best regards,
Felix Moessbauer
Siemens AG
> Patch 4: Enable the "cpuset.cpus.partition" file to show the reason
> that causes invalid partition like "root invalid (No cpu available
> due to hotplug)".
>
> Patch 5 updates the cgroup-v2.rst file accordingly. Patch 6 adds a new
> cpuset test to test the new cpuset partition code.
next prev parent reply other threads:[~2021-11-10 11:20 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 14:36 [PATCH v8 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-10-18 14:36 ` [PATCH v8 1/6] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective Waiman Long
2021-10-18 14:36 ` [PATCH v8 2/6] cgroup/cpuset: Refining features and constraints of a partition Waiman Long
2021-10-18 14:36 ` [PATCH v8 3/6] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2021-10-18 14:36 ` [PATCH v8 4/6] cgroup/cpuset: Show invalid partition reason string Waiman Long
2021-10-18 14:36 ` [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-11-15 19:31 ` Michal Koutný
2021-11-15 20:11 ` Tejun Heo
2021-11-15 21:27 ` Waiman Long
2021-11-15 21:10 ` Waiman Long
2021-11-16 17:54 ` Michal Koutný
2021-11-30 15:35 ` Waiman Long
2021-11-30 17:11 ` Tejun Heo
2021-12-01 3:56 ` Waiman Long
2021-12-01 14:13 ` Michal Koutný
2021-12-01 14:56 ` Waiman Long
2021-12-01 16:39 ` Tejun Heo
2021-12-01 17:49 ` Waiman Long
2021-12-01 14:26 ` Waiman Long
2021-12-01 16:46 ` Tejun Heo
2021-12-01 18:05 ` Waiman Long
2021-12-02 1:28 ` Waiman Long
2021-12-03 18:25 ` Michal Koutný
2021-12-03 19:27 ` Waiman Long
2021-10-18 14:36 ` [PATCH v8 6/6] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
2021-10-27 23:05 ` [PATCH v8 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-11-10 11:13 ` Felix Moessbauer [this message]
2021-11-10 13:21 ` Marcelo Tosatti
2021-11-10 13:56 ` Michal Koutný
2021-11-10 15:21 ` Moessbauer, Felix
2021-11-10 16:10 ` Marcelo Tosatti
2021-11-10 16:14 ` Marcelo Tosatti
2021-11-10 16:15 ` Jan Kiszka
2021-11-10 17:29 ` Marcelo Tosatti
2021-11-10 18:30 ` Waiman Long
2021-11-10 17:52 ` Michal Koutný
2021-11-10 18:04 ` Jan Kiszka
2021-11-10 18:15 ` Michal Koutný
2021-11-10 15:20 ` Waiman Long
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