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Date: Mon, 11 Nov 2024 12:37:56 +0000
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Subject: Re: [RFC 2/3] tick-sched: Keep tick on if hrtimer is due imminently
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
 linux-kernel@vger.kernel.org, Anna-Maria Behnsen <anna-maria@linutronix.de>,
 Frederic Weisbecker <frederic@kernel.org>, Ingo Molnar <mingo@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>
References: <20241108174839.1016424-1-joel@joelfernandes.org>
 <20241108174839.1016424-3-joel@joelfernandes.org>
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From: Christian Loehle <christian.loehle@arm.com>
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On 11/8/24 17:48, Joel Fernandes (Google) wrote:
> In highres mode, the kernel only considers timer wheel events when
> considering whether to keep the tick on (via get_next_interrupt()).
> 
> This seems odd because it consider several other reasons to keep the
> tick on. Further, turning off the tick does not help because once idle
> exit happens due to that imminent hrtimer interrupt, the tick hrtimer
> interrupt is requeued. That means more hrtimer rbtree operations for not
> much benefit.
> 
> Ideally we should not have to do anything because the cpuidle governor
> should not try to the stop the tick because it knows about this
> situation, but apparently it still does try to stop the tick.

Any details on this? Which governor?