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From:   Ivan Kozik <ivan@ludios.org>
Date:   Sun, 29 May 2022 23:52:42 +0000
Message-ID: <CAKynti+AtijnHPG-hR-zDM9eCX9HawLgB+p2C9VzS8GN-4+UsQ@mail.gmail.com>
Subject: 5.18 missing /proc/sys/kernel/sched_autogroup_enabled?
To:     linux-kernel@vger.kernel.org
Cc:     nizhen@uniontech.com, peterz@infradead.org, mingo@kernel.org
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Hello,

I noticed that /proc/sys/kernel/sched_autogroup_enabled seems to have
gone missing in 5.18. Am I doing something wrong, or is this a
regression?

I also noticed that booting 5.18 with "noautogroup" results in a
"kernel: failed when register_sysctl sched_autogroup_sysctls to
kernel" message.  Because of the error and the missing
/proc/sys/kernel/sched_autogroup_enabled, it is unclear whether
autogroup is enabled or not.

Please see below for my testing. These kernels came from
https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.18/ but I saw the
same thing with a 5.18.0 on NixOS.

Best regards,

Ivan


5.17, default:

at@ubuntu2204:~$ uname -a
Linux ubuntu2204 5.17.11-051711-generic #202205251331 SMP PREEMPT Wed
May 25 13:57:33 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

at@ubuntu2204:~$ journalctl -b | grep -i autogroup

at@ubuntu2204:~$ cat /proc/sys/kernel/sched_autogroup_enabled
1


5.17, noautogroup:

at@ubuntu2204:~$ uname -a
Linux ubuntu2204 5.17.11-051711-generic #202205251331 SMP PREEMPT Wed
May 25 13:57:33 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

at@ubuntu2204:~$ journalctl -b | grep -i autogroup
May 29 15:58:17 ubuntu2204 kernel: Command line:
BOOT_IMAGE=/boot/vmlinuz-5.17.11-051711-generic
root=UUID=20672a55-02fc-49b3-8c04-bd040f068096 ro
find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
quiet splash noautogroup
May 29 15:58:17 ubuntu2204 kernel: Kernel command line:
BOOT_IMAGE=/boot/vmlinuz-5.17.11-051711-generic
root=UUID=20672a55-02fc-49b3-8c04-bd040f068096 ro
find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
quiet splash noautogroup

at@ubuntu2204:~$ cat /proc/sys/kernel/sched_autogroup_enabled
0


5.18, default:

at@ubuntu2204:~$ uname -a
Linux ubuntu2204 5.18.0-051800-generic #202205222030 SMP
PREEMPT_DYNAMIC Sun May 22 20:33:46 UTC 2022 x86_64 x86_64 x86_64
GNU/Linux

at@ubuntu2204:~$ journalctl -b | grep -i autogroup

at@ubuntu2204:~$ cat /proc/sys/kernel/sched_autogroup_enabled
cat: /proc/sys/kernel/sched_autogroup_enabled: No such file or directory

root@ubuntu2204:~# sysctl -a | grep -i autogroup


5.18, noautogroup:

at@ubuntu2204:~$ uname -a
Linux ubuntu2204 5.18.0-051800-generic #202205222030 SMP
PREEMPT_DYNAMIC Sun May 22 20:33:46 UTC 2022 x86_64 x86_64 x86_64
GNU/Linux

at@ubuntu2204:~$ journalctl -b | grep -i autogroup
May 29 15:53:17 ubuntu2204 kernel: Command line:
BOOT_IMAGE=/boot/vmlinuz-5.18.0-051800-generic
root=UUID=20672a55-02fc-49b3-8c04-bd040f068096 ro
find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
quiet splash noautogroup
May 29 15:53:17 ubuntu2204 kernel: Kernel command line:
BOOT_IMAGE=/boot/vmlinuz-5.18.0-051800-generic
root=UUID=20672a55-02fc-49b3-8c04-bd040f068096 ro
find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
quiet splash noautogroup
May 29 15:53:17 ubuntu2204 kernel: failed when register_sysctl
sched_autogroup_sysctls to kernel

at@ubuntu2204:~$ cat /proc/sys/kernel/sched_autogroup_enabled
cat: /proc/sys/kernel/sched_autogroup_enabled: No such file or directory


root@ubuntu2204:~# cat /boot/config-5.1[78]* | grep -i config_sysctl=
CONFIG_SYSCTL=y
CONFIG_SYSCTL=y

root@ubuntu2204:~# cat /boot/config-5.1[78]* | grep -i autogroup
CONFIG_SCHED_AUTOGROUP=y
CONFIG_SCHED_AUTOGROUP=y