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[v4,3/4] sh: defconfig: drop RT_GROUP_SCHED=y from sdk7786/urquell

Message ID 20250115-fix-riscv-rt_group_sched-v4-3-607606fe73a5@coelacanthus.name
State Handled Elsewhere
Headers show
Series defconfig: drop RT_GROUP_SCHED=y | expand

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

Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
---
 arch/sh/configs/sdk7786_defconfig | 1 -
 arch/sh/configs/urquell_defconfig | 1 -
 2 files changed, 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig
index 07894f13441ef622c3af8d8f4b5770c2ab66bcd8..7a6efd5b4a62463381005072a679a8ce022a2ef9 100644
--- a/arch/sh/configs/sdk7786_defconfig
+++ b/arch/sh/configs/sdk7786_defconfig
@@ -17,7 +17,6 @@  CONFIG_CPUSETS=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_BLK_CGROUP=y
 CONFIG_RELAY=y
 CONFIG_NAMESPACES=y
diff --git a/arch/sh/configs/urquell_defconfig b/arch/sh/configs/urquell_defconfig
index 00ef62133b04ded8d0b4221f11e0adafde99d386..9cf4a719001ea5ef4b031c1bbbf8098e8af5a2b2 100644
--- a/arch/sh/configs/urquell_defconfig
+++ b/arch/sh/configs/urquell_defconfig
@@ -15,7 +15,6 @@  CONFIG_CPUSETS=y
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
-CONFIG_RT_GROUP_SCHED=y
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_PROFILING=y
 CONFIG_MODULES=y