Re: [PATCH 6/6] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2855/tegra/omap2plus

[Stefan Wahren <wahrenst@gmx.net>]

Hi Celeste,

there is a typo in the subject line

s/bcm2855/bcm2835

Am 09.07.24 um 01:49 schrieb Kevin Hilman:
> Celeste Liu <coelacanthushex@gmail.com> writes:
>
>> Commit 673ce00c5d6c ("ARM: omap2plus_defconfig: Add support for distros
>> with systemd") said it's because of recommendation from systemd. But
>> systemd changed their recommendation later.[1]
>>
>> For cgroup v1, if turned on, and there's any cgroup in the "cpu" hierarchy it
>> needs an RT budget assigned, otherwise the processes in it will not be able to
>> get RT at all. The problem with RT group scheduling is that it requires the
>> budget assigned but there's no way we could assign a default budget, since the
>> values to assign are both upper and lower time limits, are absolute, and need to
>> be sum up to < 1 for each individal cgroup. That means we cannot really come up
>> with values that would work by default in the general case.[2]
>>
>> For cgroup v2, it's almost unusable as well. If it turned on, the cpu controller
>> can only be enabled when all RT processes are in the root cgroup. But it will
>> lose the benefits of cgroup v2 if all RT process were placed in the same cgroup.
>>
>> Red Hat, Gentoo, Arch Linux and Debian all disable it. systemd also doesn't
>> support it.
>>
>> [1]: https://github.com/systemd/systemd/commit/f4e74be1856b3ac058acbf1be321c31d5299f69f
>> [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700
>>
>> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com>
>> ---
>>   arch/arm/configs/bcm2835_defconfig   | 1 -
>>   arch/arm/configs/omap2plus_defconfig | 1 -
>>   arch/arm/configs/tegra_defconfig     | 1 -
> For omap2plus_defconfig:
>
> Acked-by: Kevin Hilman <khilman@baylibre.com>
>
>
For bcm2835_defconfig:

Tested-by: Stefan Wahren <wahrenst@gmx.net>