linux-kernel - Re: stable: commit "cpuidle: menu: Avoid discarding useful information" causes regressions

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Message-ID: <2025101421-citrus-barley-9061@gregkh>
Date: Tue, 14 Oct 2025 10:02:41 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	Christian Loehle <christian.loehle@....com>,
	Sasha Levin <sashal@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tomasz Figa <tfiga@...omium.org>, stable@...r.kernel.org
Subject: Re: stable: commit "cpuidle: menu: Avoid discarding useful
 information" causes regressions

On Tue, Oct 14, 2025 at 04:54:45PM +0900, Sergey Senozhatsky wrote:
> On (25/10/14 09:47), Greg Kroah-Hartman wrote:
> > On Tue, Oct 14, 2025 at 04:43:43PM +0900, Sergey Senozhatsky wrote:
> > > Hello,
> > > 
> > > We are observing performance regressions (cpu usage, power
> > > consumption, dropped frames in video playback test, etc.)
> > > after updating to recent stable kernels.  We tracked it down
> > > to commit 3cd2aa93674e in linux-6.1.y and commit 3cd2aa93674
> > > in linux-6.6.y ("cpuidle: menu: Avoid discarding useful information",
> > > upstream commit 85975daeaa4).
> > > 
> > > Upstream fixup fa3fa55de0d ("cpuidle: governors: menu: Avoid using
> > > invalid recent intervals data") doesn't address the problems we are
> > > observing.  Revert seems to be bringing performance metrics back to
> > > pre-regression levels.
> > > 
> > 
> > For some reason that commit was not added to the 6.1 releases, sorry
> > about that.  Can you submit a working/tested backport so we can queue it
> > up after the next round of releases in a few days?
> 
> Sorry for the confusion, the commit in question presents both in
> stable 6.1 and in 6.6 and appears to be causing regressions on our
> tests.  I copy-pasted wrong commit id for 6.1: it should be a9edb700846
> for 6.1 (and 3cd2aa93674 for 6.6).
> 

The point is still the same, commit fa3fa55de0d6 ("cpuidle: governors:
menu: Avoid using invalid recent intervals data"), is not backported to
6.1.y, it is however in the following released kernels:
	5.10.241 5.15.190 6.6.103 6.12.43 6.15.11 6.16.2 6.17
so something got lost in our trees and it needs to be backported.

I need to knock up a "what patches are missing" script again and sweep
the trees to catch these types of things.  It's been a year or so since
I last did that.

thanks,

greg k-h