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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Jens Axboe <axboe@kernel.dk>, Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
 linux-pm@vger.kernel.org, daniel.lezcano@linaro.org,
 "Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH 4/4] sched/core: split iowait state into two states
Date: Thu, 25 Apr 2024 16:20:29 +0200
Message-ID: <8409301.NyiUUSuA9g@kreacher>
In-Reply-To: <20240424100127.GV40213@noisy.programming.kicks-ass.net>
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 <20240416121526.67022-5-axboe@kernel.dk>
 <20240424100127.GV40213@noisy.programming.kicks-ass.net>
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On Wednesday, April 24, 2024 12:01:27 PM CEST Peter Zijlstra wrote:
> On Tue, Apr 16, 2024 at 06:11:21AM -0600, Jens Axboe wrote:
> > iowait is a bogus metric, but it's helpful in the sense that it allows
> > short waits to not enter sleep states that have a higher exit latency
> > than would've otherwise have been picked for iowait'ing tasks. However,
> > it's harmless in that lots of applications and monitoring assumes that
> > iowait is busy time, or otherwise use it as a health metric.
> > Particularly for async IO it's entirely nonsensical.
> 
> Let me get this straight, all of this is about working around
> cpuidle menu governor insaity?
> 
> Rafael, how far along are we with fully deprecating that thing? Yes it
> still exists, but should people really be using it still?

Well, they appear to be used to it ...