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>
Subject: Re: [PATCH 3/5] cgroup/cpuset: Find another usable CPU if none found in current cpuset
Date: Fri, 17 Mar 2023 13:27:08 +0100 [thread overview]
Message-ID: <20230317122708.ax3m2d4zijkfdzjq@blackpad> (raw)
In-Reply-To: <58a1a878-fa0b-285d-3e43-2b5103d3c770@redhat.com>
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On Tue, Mar 14, 2023 at 04:22:06PM -0400, Waiman Long <longman@redhat.com> wrote:
> Some arm64 systems can have asymmetric CPUs where certain tasks are only
> runnable on a selected subset of CPUs.
Ah, I'm catching up.
> This information is not captured in the cpuset. As a result,
> task_cpu_possible_mask() may return a mask that have no overlap with
> effective_cpus causing new_cpus to become empty.
I can see that historically, there was an approach of terminating
unaccomodable tasks:
94f9c00f6460 ("arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores")
the removal of killing had been made possible with
df950811f4a8 ("arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system").
That gives two other alternatives to affinity modification:
2) kill such tasks (not unlike OOM upon memory.max reduction),
3) reject cpuset reduction (violates cgroup v2 delegation).
What do you think about 2)?
Michal
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next prev parent reply other threads:[~2023-03-17 12:27 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 20:08 [PATCH 0/5] cgroup/cpuset: Miscellaneous updates Waiman Long
2023-03-06 20:08 ` [PATCH 1/5] cgroup/cpuset: Skip task update if hotplug doesn't affect current cpuset Waiman Long
2023-03-14 16:50 ` Michal Koutný
2023-03-14 18:20 ` Waiman Long
2023-03-06 20:08 ` [PATCH 2/5] cgroup/cpuset: Include offline CPUs when tasks' cpumasks in top_cpuset are updated Waiman Long
2023-03-14 17:34 ` Michal Koutný
2023-03-14 19:02 ` Waiman Long
2023-03-15 10:06 ` Michal Koutný
2023-03-15 14:39 ` Waiman Long
2023-03-06 20:08 ` [PATCH 3/5] cgroup/cpuset: Find another usable CPU if none found in current cpuset Waiman Long
2023-03-14 18:17 ` Michal Koutný
2023-03-14 20:22 ` Waiman Long
2023-03-17 12:27 ` Michal Koutný [this message]
2023-03-17 14:59 ` Waiman Long
2023-03-24 14:32 ` Will Deacon
2023-03-24 14:42 ` Waiman Long
2023-03-24 18:19 ` Michal Koutný
2023-03-25 22:08 ` Waiman Long
2023-03-06 20:08 ` [PATCH 4/5] cgroup/cpuset: Add CONFIG_DEBUG_CPUSETS config for cpuset testing Waiman Long
2023-03-06 20:08 ` [PATCH 5/5] cgroup/cpuset: Minor updates to test_cpuset_prs.sh Waiman Long
2023-03-07 16:16 ` Kamalesh Babulal
2023-03-15 16:24 ` [PATCH 0/5] cgroup/cpuset: Miscellaneous updates Will Deacon
2023-03-15 16:59 ` Waiman Long
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