From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: "Tejun Heo" <tj@kernel.org>, "Zefan Li" <lizefan.x@bytedance.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <shuah@kernel.org>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Roman Gushchin" <guro@fb.com>, "Phil Auld" <pauld@redhat.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"Michal Koutný" <mkoutny@suse.com>
Subject: Re: [PATCH v9 4/7] cgroup/cpuset: Add a new isolated cpus.partition type
Date: Wed, 12 Jan 2022 16:21:00 +0100 [thread overview]
Message-ID: <Yd7x3P+wGCVfYtza@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20211205183220.818872-5-longman@redhat.com>
On Sun, Dec 05, 2021 at 01:32:17PM -0500, Waiman Long wrote:
> Cpuset v1 uses the sched_load_balance control file to determine if load
> balancing should be enabled. Cpuset v2 gets rid of sched_load_balance
> as its use may require disabling load balancing at cgroup root.
>
> For workloads that require very low latency like DPDK, the latency
> jitters caused by periodic load balancing may exceed the desired
> latency limit.
>
> When cpuset v2 is in use, the only way to avoid this latency cost is to
> use the "isolcpus=" kernel boot option to isolate a set of CPUs. After
> the kernel boot, however, there is no way to add or remove CPUs from
> this isolated set. For workloads that are more dynamic in nature, that
> means users have to provision enough CPUs for the worst case situation
> resulting in excess idle CPUs.
>
> To address this issue for cpuset v2, a new cpuset.cpus.partition type
> "isolated" is added which allows the creation of a cpuset partition
> without load balancing. This will allow system administrators to
> dynamically adjust the size of isolated partition to the current need
> of the workload without rebooting the system.
you can, ofcourse, create lots of 1 cpu partitions, which is effectively
what you're doing, except there was a problem with that which you also
forgot to mention.
next prev parent reply other threads:[~2022-01-12 15:21 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-05 18:32 [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-12-05 18:32 ` [PATCH v9 1/7] cgroup/cpuset: Don't let child cpusets restrict parent in default hierarchy Waiman Long
2021-12-13 20:41 ` Tejun Heo
2021-12-15 12:23 ` Michal Koutný
2021-12-15 17:59 ` Waiman Long
2021-12-17 15:48 ` [PATCH] cgroup/cpuset: Make child cpusets restrict parents on v1 hierarchy Michal Koutný
2021-12-17 16:34 ` Waiman Long
2022-01-12 21:25 ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 2/7] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective Waiman Long
2021-12-13 20:45 ` Tejun Heo
2021-12-15 3:24 ` Waiman Long
2021-12-15 10:36 ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 3/7] cgroup/cpuset: Refining features and constraints of a partition Waiman Long
2021-12-15 14:49 ` Michal Koutný
2021-12-15 16:29 ` Waiman Long
2021-12-16 9:28 ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 4/7] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2022-01-12 15:21 ` Peter Zijlstra [this message]
2022-01-12 15:40 ` Waiman Long
2022-01-12 21:23 ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 5/7] cgroup/cpuset: Show invalid partition reason string Waiman Long
2021-12-05 18:32 ` [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-12-13 21:00 ` Tejun Heo
2021-12-15 14:44 ` Michal Koutný
2021-12-15 18:16 ` Waiman Long
2021-12-15 18:35 ` Tejun Heo
2021-12-15 18:55 ` Waiman Long
2022-01-12 21:21 ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 7/7] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
2021-12-09 15:39 ` [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
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