linux-kernel - Re: [PATCH v2 3/4] sched, psi: Don't account irq time if sched_clock

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Message-ID: <20241008140437.GA6937@cmpxchg.org>
Date: Tue, 8 Oct 2024 10:04:37 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Yafang Shao <laoar.shao@...il.com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, surenb@...gle.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] sched, psi: Don't account irq time if
 sched_clock_irqtime is disabled

On Tue, Oct 08, 2024 at 02:19:50PM +0800, Yafang Shao wrote:
> sched_clock_irqtime may be disabled due to the clock source, in which case
> IRQ time should not be accounted. Let's add a conditional check to avoid
> unnecessary logic.

Makes sense. When disabled, irq_time_read() won't change over time, so
there is nothing to account. We can save iterating the whole hierarchy
on every tick and context switch.

> Signed-off-by: Yafang Shao <laoar.shao@...il.com>

Acked-by: Johannes Weiner <hannes@...xchg.org>