| Message ID | 20240530111947.549474-10-CoelacanthusHex@gmail.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | defconfig: drop RT_GROUP_SCHED=y | expand |
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@gmail.com> As a distro maintainer who had once been bitten by this option: Reviewed-by: Xi Ruoyao <xry111@xry111.site> > --- > 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
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
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@gmail.com> --- arch/loongarch/configs/loongson3_defconfig | 1 - 1 file changed, 1 deletion(-)