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From: Hillf Danton <hdanton@sina.com>
To: Benjamin Segall <bsegall@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
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	Boqun Feng <boqun.feng@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] locking/percpu-rwsem: do not do lock handoff in percpu_up_write
Date: Tue, 30 Jan 2024 19:41:56 +0800
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On Mon, 29 Jan 2024 12:36:20 -0800 Benjamin Segall <bsegall@google.com>
> 
> The basic locking issue was due to userspace rapidly spawning threads
> (or processes) more rapidly than the cpus they are running on can
> support, and this causing issues for unrelated threads doing cgroup
> operations on other cpus.
> 
> The contention can be due to a combination of just straight up spawning
> way too many, userspace misconfiguration of cpus allowed, or load
> balancer weaknesses. (If you pick minimum cpu.shares values and have
> large machines, SCHED_LOAD_RESOLUTION isn't really enough for load
> balance to do a good job, and what you're telling the load balancer you
> want isn't really a good idea in the first place).

Sigh, add change to percpu-rwsem's handoff because cgroup has a cough
in chest.