Re: [PATCH v4 4/4] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2835/tegra/omap2plus

[Florian Fainelli <florian.fainelli@broadcom.com>]

On 1/14/25 12:41, Celeste Liu wrote:
> 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
> 
> Tested-by: Stefan Wahren <wahrenst@gmx.net>
> Acked-by: Kevin Hilman <khilman@baylibre.com>
> Acked-by: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
> ---
>   arch/arm/configs/bcm2835_defconfig   | 1 -

Acked-by: Florian Fainelli <florian.fainelli@broadcom.com> # 
bcm2835_defconfig
-- 
Florian