From: Peter Zijlstra <peterz@infradead.org>
To: Jing Wu <realwujing@gmail.com>
Cc: Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
linux-kernel@vger.kernel.org,
Qiliang Yuan <yuanql9@chinatelecom.cn>,
Jian Zhang <zhangj332@chinatelecom.cn>
Subject: Re: [PATCH] x86/aperfmperf: Refresh stale sample via IPI for busy NOHZ_FULL CPUs
Date: Tue, 28 Jul 2026 15:44:34 +0200 [thread overview]
Message-ID: <20260728134434.GU751831@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260728-bug-isolatecpu-cpufreq-v1-1-e95d34db8bcd@gmail.com>
On Tue, Jul 28, 2026 at 07:27:54PM +0800, Jing Wu wrote:
> An isolated CPU covered by nohz_full stops its periodic tick once it
> has only one runnable task, since sched_can_stop_tick() only checks
> scheduling-class fairness and has no notion of cpufreq reporting
> needs. arch_scale_freq_tick() runs only from scheduler_tick(), so
> cpu_samples for that CPU is never refreshed again.
Sending IPIs to NOHZ_FULL Cpus should be a no-no.
next prev parent reply other threads:[~2026-07-28 13:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-28 11:27 [PATCH] x86/aperfmperf: Refresh stale sample via IPI for busy NOHZ_FULL CPUs Jing Wu
2026-07-28 13:44 ` Peter Zijlstra [this message]
2026-07-28 14:42 ` Peter Zijlstra
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