linux-kernel - Re: [PATCH] profiling: remove prof_cpu

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Message-ID: <503c1a50-ddc0-4128-b0f0-feceb43ff5d3@I-love.SAKURA.ne.jp>
Date: Sun, 28 Jul 2024 08:47:55 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc: Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>, Peter Zijlstra <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>, Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] profiling: remove prof_cpu_mask

On 2024/07/28 6:22, Linus Torvalds wrote:
> I wonder how many people actually use this ancient kernel profiling
> thing. I get the feeling that it's "one real user and a hundred syzbot
> test failures".

What about emitting some kernel messages for investigating whether there
are users who need this code, and wait for two years for whether someone
says "I need this code" ?

For example, hfs ( https://syzkaller.appspot.com/upstream/s/hfs ) has
many open bugs. Some of them have patches but nobody can review/take them.
Unless a filesystem needs to be mounted as a native filesystem, I think
that re-implementing such filesystem as a fuse-based filesystem will help
reducing overall bugs.

Anyway, it seems that the kernel sleep profiling is no longer working
after commit 42a20f86dc19 ("sched: Add wrapper for get_wchan() to keep
task blocked").