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From: Thorsten Leemhuis <regressions@leemhuis.info>
To: Greg KH <greg@kroah.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Jon Hunter <jonathanh@nvidia.com>,
	mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	dietmar.eggemann@arm.com, rostedt@goodmis.org,
	bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
	vschneid@redhat.com, wkarny@gmail.com, qyousef@layalina.io,
	tglx@linutronix.de, rafael@kernel.org, viresh.kumar@linaro.org,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
	Thierry Reding <treding@nvidia.com>,
	Sasha Levin <sashal@nvidia.com>,
	Laxman Dewangan <ldewangan@nvidia.com>,
	Shardar Mohammed <smohammed@nvidia.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Linux kernel regressions list <regressions@lists.linux.dev>
Subject: Re: [PATCH] sched/fair: Fix frequency selection for non invariant case
Date: Thu, 15 Feb 2024 11:00:39 +0100	[thread overview]
Message-ID: <9a74676c-0032-4f29-84aa-c91e5ef01aae@leemhuis.info> (raw)
In-Reply-To: <2024021545-rise-plot-24c3@gregkh>

On 15.02.24 10:13, Greg KH wrote:
> On Thu, Feb 15, 2024 at 09:45:01AM +0100, Thorsten Leemhuis wrote:
>> Linus, what...
>>
>> On 14.02.24 18:22, Vincent Guittot wrote:
>>> On Wed, 14 Feb 2024 at 18:20, Linus Torvalds
>>> <torvalds@linux-foundation.org> wrote:
>>>> On Wed, 14 Feb 2024 at 09:12, Jon Hunter <jonathanh@nvidia.com> wrote:
>>>>> We have also observed a performance degradation on our Tegra platforms
>>>>> with v6.8-rc1. Unfortunately, the above change does not fix the problem
>>>>> for us and we are still seeing a performance issue with v6.8-rc4. For
>>>>> example, running Dhrystone on Tegra234 I am seeing the following ...
>>>>> [...]
>>>>> If I revert this change and the following ...
>>>>>   b3edde44e5d4 ("cpufreq/schedutil: Use a fixed reference frequency")
>>>>>   f12560779f9d ("sched/cpufreq: Rework iowait boost")
>>>>>   9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor
>>>>> ... then the perf is similar to where it was ...
>>>>
>>>> Ok, guys, this whole scheduler / cpufreq rewrite seems to have been
>>>> completely buggered.
>>>> [...]
>>> This should fix it:
>>> https://lore.kernel.org/lkml/20240117190545.596057-1-vincent.guittot@linaro.org/
>>
>> ...do you want me to do in situations like this? I'm asking, as I see
>> situations like this frequently -- e.g. people reporting problems a
>> second, third, or fourth time while the fix is already sitting in -next
>> for a few days.
>>
>> Want me to list them in the weekly reports so that you can cherry-pick
>> them from -next if you want?
> 
> Poke the maintainer to get off their butt and submit the pull request to
> Linus 

Well, I did that sometimes and will continue to do so. But some
maintainers then feel pestered and become annoyed by my efforts -- which
in the long-term is counter productive, as regression tracking will only
work well if maintainers and I work well together. That's why I'm a bit
careful with such things (side note: don't worry, I know that some
conflict is inevitable -- but I don't have your or Linus standing, so I
have to choose my fights carefully...).

I sometimes also got replies along the lines of "we are only at -rc2,
this can wait till -rc5 or -rc6" -- and I have no quote from Linus at
hand I can point maintainers to that says something along the lines of
"if a regression fix was in -next for at least two days, submit it to
mainline before the next -rc, unless there is a strong reason why that
particular fix needs more testing" (or whatever he actually wants).

> (note, this is me in this case...)
> I'll get it into the next -rc, sorry for the delay, other things got in
> the way, my fault.

Happens, I don't care too much about this specific event, more about the
general problem. Especially the -mm tree bugs me sometimes, as I noticed
that Andrew often lets regression fixes linger in -next for round about
a week; he furthermore sometimes sends this stuff to Linus on Mondays or
Tuesdays. Due to that the fixes often miss at least one, sometimes two
-rcs. That is especially hard to watch if the regression made it to a
stable kernel and you are waiting for the fix to get mainlined.

Ciao, Thorsten

      reply	other threads:[~2024-02-15 10:00 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-14 18:36 [PATCH] sched/fair: Fix frequency selection for non invariant case Vincent Guittot
2024-01-15 12:15 ` Qais Yousef
2024-01-15 20:06 ` Dietmar Eggemann
2024-01-16  9:59 ` Ingo Molnar
2024-01-16 10:04   ` Vincent Guittot
2024-01-17 14:28   ` Thorsten Leemhuis
2024-02-14 17:12 ` Jon Hunter
2024-02-14 17:19   ` Vincent Guittot
2024-02-14 17:19   ` Linus Torvalds
2024-02-14 17:22     ` Vincent Guittot
2024-02-14 17:57       ` Jon Hunter
2024-02-15  8:45       ` Thorsten Leemhuis
2024-02-15  9:13         ` Greg KH
2024-02-15 10:00           ` Thorsten Leemhuis [this message]

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