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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <nd64xabhbb53bbqoxsjkfvkmlpn5tkdlu3nb5ofwdhyauko35b@qv6in7biupgi>
Date: Tue, 14 Oct 2025 20:55:42 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Christian Loehle <christian.loehle@....com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.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 (25/10/14 11:25), Christian Loehle wrote:
> On 10/14/25 11:23, Sergey Senozhatsky wrote:
> > On (25/10/14 10:50), Christian Loehle wrote:
> >>> 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.
> >>
> >> Any details would be much appreciated.
> >> How do the idle state usages differ with and without
> >> "cpuidle: menu: Avoid discarding useful information"?
> >> What do the idle states look like in your platform?
> > 
> > Sure, I can run tests.  How do I get the numbers/stats
> > that you are asking for?
> 
> Ideally just dump
> cat /sys/devices/system/cpu/cpu*/cpuidle/state*/*
> before and after the test.

OK, got some data for you.  The terminology being used here is as follows:

- 6.1-base
  is 6.1 stable with a9edb700846 "cpuidle: menu: Avoid discarding useful information"

- 6.1-base-fixup
  is 6.1 stable with a9edb700846 and fa3fa55de0d6 "cpuidle: governors:
  menu: Avoid using invalid recent intervals data" cherry-pick

- 6.1-revert
  is 6.1 stable with a9edb700846 reverted (and no fixup commit, obviously)

Just to show the scale of regression, results of some of the benchmarks:

  6.1-base:		84.5
  6.1-base-fixup:	76.5
  6.1-revert:		59.5

  (lower is better, 6.1-revert has the same results as previous stable
  kernels).

Please find  /sys/devices/system/cpu/cpu*/cpuidle/state*/* dumps
attached (6 files).

The cpuidle/state*/* directory structure is as follows (NOTE: dumps
don't contain s2idle subdirs):

/sys/devices/system/cpu/cpu1/cpuidle/
|-- state0
|   |-- above
|   |-- below
|   |-- default_status
|   |-- desc
|   |-- disable
|   |-- latency
|   |-- name
|   |-- power
|   |-- rejected
|   |-- residency
|   |-- time
|   `-- usage
|-- state1
|   |-- above
|   |-- below
|   |-- default_status
|   |-- desc
|   |-- disable
|   |-- latency
|   |-- name
|   |-- power
|   |-- rejected
|   |-- residency
|   |-- s2idle
|   |   |-- time
|   |   `-- usage
|   |-- time
|   `-- usage
|-- state2
|   |-- above
|   |-- below
|   |-- default_status
|   |-- desc
|   |-- disable
|   |-- latency
|   |-- name
|   |-- power
|   |-- rejected
|   |-- residency
|   |-- s2idle
|   |   |-- time
|   |   `-- usage
|   |-- time
|   `-- usage
`-- state3
    |-- above
    |-- below
    |-- default_status
    |-- desc
    |-- disable
    |-- latency
    |-- name
    |-- power
    |-- rejected
    |-- residency
    |-- s2idle
    |   |-- time
    |   `-- usage
    |-- time
    `-- usage

Hope this helps.

View attachment "6.1-base-after-test" of type "text/plain" (1204 bytes)

View attachment "6.1-base-before-test" of type "text/plain" (1120 bytes)

View attachment "6.1-base-fixup-after-test" of type "text/plain" (1205 bytes)

View attachment "6.1-base-fixup-before-test" of type "text/plain" (1125 bytes)

View attachment "6.1-revert-after-test" of type "text/plain" (1206 bytes)

View attachment "6.1-revert-before-test" of type "text/plain" (1143 bytes)