Re: [PATCH 2/6] loongarch: defconfig: drop RT_GROUP_SCHED=y

[Xi Ruoyao]

On Thu, 2024-05-30 at 19:19 +0800, Celeste Liu wrote:
> 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.[1]
> 
> 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.[2]
> 
> [1]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700
> [2]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383
> 
> Signed-off-by: Celeste Liu <CoelacanthusHex@xxxxxxxxx>

As a distro maintainer who had once been bitten by this option:

Reviewed-by: Xi Ruoyao <xry111@xxxxxxxxxxx>

> ---
>  arch/loongarch/configs/loongson3_defconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
> index b4252c357c8e..4d93adb3f1a2 100644
> --- a/arch/loongarch/configs/loongson3_defconfig
> +++ b/arch/loongarch/configs/loongson3_defconfig
> @@ -23,7 +23,6 @@ CONFIG_NUMA_BALANCING=y
>  CONFIG_MEMCG=y
>  CONFIG_BLK_CGROUP=y
>  CONFIG_CFS_BANDWIDTH=y
> -CONFIG_RT_GROUP_SCHED=y
>  CONFIG_CGROUP_PIDS=y
>  CONFIG_CGROUP_RDMA=y
>  CONFIG_CGROUP_FREEZER=y

-- 
Xi Ruoyao <xry111@xxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University