| Message ID | 20240910-fix-riscv-rt_group_sched-v3-1-486e75e5ae6d@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | defconfig: drop RT_GROUP_SCHED=y | expand |
On Tue, Sep 10, 2024 at 08:51:07PM +0800, Celeste Liu wrote: > Commit ba6cfef057e1 ("riscv: enable Docker requirements in defconfig") > introduced it because of Docker, but Docker has removed this requirement > since [1] (2023-04-19). > > 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.[3] > > [1]: https://github.com/moby/moby/commit/005150ed69c540fb0b5323e0f2208608c1204536 > [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700 > [3]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383 > > Acked-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> > Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> Acked-by: Charlie Jenkins <charlie@rivosinc.com> > --- > arch/riscv/configs/defconfig | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig > index 12dc8c73a8acfaa5c8f442968a807de303428d9e..de85c3ab261e6d62b2089a3c89bdc9d1b34fa792 100644 > --- a/arch/riscv/configs/defconfig > +++ b/arch/riscv/configs/defconfig > @@ -9,7 +9,6 @@ CONFIG_CGROUPS=y > CONFIG_MEMCG=y > CONFIG_CGROUP_SCHED=y > CONFIG_CFS_BANDWIDTH=y > -CONFIG_RT_GROUP_SCHED=y > CONFIG_CGROUP_PIDS=y > CONFIG_CGROUP_FREEZER=y > CONFIG_CGROUP_HUGETLB=y > > -- > 2.46.0 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig index 12dc8c73a8acfaa5c8f442968a807de303428d9e..de85c3ab261e6d62b2089a3c89bdc9d1b34fa792 100644 --- a/arch/riscv/configs/defconfig +++ b/arch/riscv/configs/defconfig @@ -9,7 +9,6 @@ CONFIG_CGROUPS=y CONFIG_MEMCG=y CONFIG_CGROUP_SCHED=y CONFIG_CFS_BANDWIDTH=y -CONFIG_RT_GROUP_SCHED=y CONFIG_CGROUP_PIDS=y CONFIG_CGROUP_FREEZER=y CONFIG_CGROUP_HUGETLB=y
Commit ba6cfef057e1 ("riscv: enable Docker requirements in defconfig") introduced it because of Docker, but Docker has removed this requirement since [1] (2023-04-19). 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.[3] [1]: https://github.com/moby/moby/commit/005150ed69c540fb0b5323e0f2208608c1204536 [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700 [3]: https://github.com/systemd/systemd/issues/13781#issuecomment-549164383 Acked-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com> Signed-off-by: Celeste Liu <CoelacanthusHex@gmail.com> --- arch/riscv/configs/defconfig | 1 - 1 file changed, 1 deletion(-)