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[v4,2/4] loongarch: defconfig: drop RT_GROUP_SCHED=y

Message ID 20250115-fix-riscv-rt_group_sched-v4-2-607606fe73a5@coelacanthus.name (mailing list archive)
State New
Headers show
Series defconfig: drop RT_GROUP_SCHED=y | expand

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conchuod/vmtest-for-next-PR success PR summary
conchuod/patch-2-test-1 success .github/scripts/patches/tests/build_rv32_defconfig.sh took 113.54s
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Commit Message

Celeste Liu Jan. 14, 2025, 8:41 p.m. UTC 
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

Reviewed-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
---
 arch/loongarch/configs/loongson3_defconfig | 1 -
 1 file changed, 1 deletion(-)
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Patch

diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
index 4dffc90192f7816074c3bd4b55c12159d5757676..4387bcec8f484173e5367456a69f6a7f03595d46 100644
--- a/arch/loongarch/configs/loongson3_defconfig
+++ b/arch/loongarch/configs/loongson3_defconfig
@@ -24,7 +24,6 @@  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