linux-kernel - Re: [PATCHSET v6 0/4] Split iowait into two states

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Message-ID: <20240904142841.GL4723@noisy.programming.kicks-ass.net>
Date: Wed, 4 Sep 2024 16:28:41 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, rafael@...nel.org,
	daniel.lezcano@...aro.org, linux-pm@...r.kernel.org
Subject: Re: [PATCHSET v6 0/4] Split iowait into two states

On Mon, Aug 19, 2024 at 09:39:45AM -0600, Jens Axboe wrote:
> Hi,
> 
> This is v6 of the patchset where the current in_iowait state is split
> into two parts:
> 
> 1) The "task is sleeping waiting on IO", and would like cpufreq goodness
>    in terms of sleep and wakeup latencies.
> 2) The above, and also accounted as such in the iowait stats.
> 
> The current ->in_iowait covers both, this series splits it into two types
> of state so that each can be controlled seperately.

Yeah, but *WHY* !?!? I have some vague memories from last time around,
but patches should really keep this information.

> Patches 1..3 are prep patches, changing the type of
> task_struct->nr_iowait and adding helpers to manipulate the iowait counts.
> 
> Patch 4 does the actual splitting.
> 
> This has been sitting for a while, would be nice to get this queued up
> for 6.12. Comments welcome!

Ufff, and all this because menu-governor does something insane :-(

Rafael, why can't we simply remove this from menu? All the nr_iowait*()
users are basically broken and I would much rather fix broken rather
than work around broken like this.

That is, from where I'm sitting this all makes the io-wait situation far
worse instead of better.