From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
"Zhou Ti (x2019cwm)" <x2019cwm@stfx.ca>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Yunfeng Ye <yeyunfeng@huawei.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Marcelo Tosatti <mtosatti@redhat.com>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 01/10] tick/nohz: Prevent tick_nohz_get_sleep_length() from returning negative value
Date: Tue, 16 Mar 2021 13:21:29 +0100 [thread overview]
Message-ID: <YFCiycIaViYCy3GH@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210311123708.23501-2-frederic@kernel.org>
On Thu, Mar 11, 2021 at 01:36:59PM +0100, Frederic Weisbecker wrote:
> From: "Zhou Ti (x2019cwm)" <x2019cwm@stfx.ca>
>
> If the hardware clock happens to fire its interrupts late, two possible
> issues can happen while calling tick_nohz_get_sleep_length(). Either:
>
> 1) The next clockevent device event is due past the last idle entry time.
>
> or:
>
> 2) The last timekeeping update happened before the last idle entry time
> and the next timer callback expires before the last idle entry time.
>
> Make sure that both cases are handled to avoid returning a negative
> duration to the cpuidle governors.
Why? ... and wouldn't it be cheaper the fix the caller to
check negative once, instead of adding two branches here?
next prev parent reply other threads:[~2021-03-16 12:39 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 12:36 [PATCH 00/10] tick/nohz updates Frederic Weisbecker
2021-03-11 12:36 ` [PATCH 01/10] tick/nohz: Prevent tick_nohz_get_sleep_length() from returning negative value Frederic Weisbecker
2021-03-16 12:21 ` Peter Zijlstra [this message]
2021-03-16 13:37 ` Frederic Weisbecker
2021-03-16 14:35 ` Peter Zijlstra
2021-03-16 14:53 ` Frederic Weisbecker
2021-03-16 15:26 ` Rafael J. Wysocki
2021-03-16 15:57 ` 回复: " Zhou Ti (x2019cwm)
2021-03-16 16:08 ` Zhou Ti (x2019cwm)
2021-03-16 16:25 ` Peter Zijlstra
2021-03-17 21:49 ` Zhou Ti (x2019cwm)
2021-03-25 13:14 ` Frederic Weisbecker
2021-03-25 18:56 ` Rafael J. Wysocki
2021-03-25 19:18 ` Zhou Ti (x2019cwm)
2021-03-25 19:50 ` Rafael J. Wysocki
2021-03-25 20:37 ` Zhou Ti (x2019cwm)
2021-03-26 17:01 ` Rafael J. Wysocki
2021-03-26 17:53 ` Zhou Ti (x2019cwm)
2021-03-26 18:54 ` Rafael J. Wysocki
2021-03-26 22:53 ` Zhou Ti (x2019cwm)
2021-03-29 12:44 ` Rafael J. Wysocki
2021-03-29 14:49 ` Zhou Ti (x2019cwm)
2021-03-11 12:37 ` [PATCH 02/10] tick/nohz: Add tick_nohz_full_this_cpu() Frederic Weisbecker
2021-03-16 12:28 ` Peter Zijlstra
2021-03-16 13:05 ` Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 03/10] tick/nohz: Conditionally restart tick on idle exit Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 04/10] tick/nohz: Remove superflous check for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 05/10] tick/nohz: Update idle_exittime on actual idle exit Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 06/10] timer: Report ignored local enqueue in nohz mode Frederic Weisbecker
2021-03-16 15:27 ` Peter Zijlstra
2021-03-25 13:07 ` Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 07/10] tick/nohz: Update nohz_full Kconfig help Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 08/10] tick/nohz: Only wakeup a single target cpu when kicking a task Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 09/10] tick/nohz: Change signal tick dependency to wakeup CPUs of member tasks Frederic Weisbecker
2021-03-11 12:37 ` [PATCH 10/10] tick/nohz: Kick only _queued_ task whose tick dependency is updated Frederic Weisbecker
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