sched/topology: Mark SD_PREFER_SIBLING as SDF_NEEDS_GROUPS (3a6712c7) · Commits · 戴 / test

SD_PREFER_SIBLING is currently considered in sd_parent_degenerate() but not in sd_degenerate(). It too hinges on load balancing, and thus won't have any effect when set on a domain with a single group. Add it to SD_DEGENERATE_GROUPS_MASK. Signed-off-by:

Valentin Schneider <valentin.schneider@arm.com> Signed-off-by:

Ingo Molnar <mingo@kernel.org> Acked-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Link: https://lore.kernel.org/r/20200817113003.20802-12-valentin.schneider@arm.com

include/linux/sched/sd_flags.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -131,8 +131,10 @@ SD_FLAG(SD_ASYM_PACKING, SDF_SHARED_CHILD)
		*
		* Set up until domains start spanning NUMA nodes. Close to being a SHARED_CHILD
		* flag, but cleared below domains with SD_ASYM_CPUCAPACITY.
		*
		* NEEDS_GROUPS: Load balancing flag.
		*/
		SD_FLAG(SD_PREFER_SIBLING, 0)
		SD_FLAG(SD_PREFER_SIBLING, SDF_NEEDS_GROUPS)

		/*
		* sched_groups of this level overlap

kernel/sched/topology.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -184,7 +184,7 @@ sd_parent_degenerate(struct sched_domain sd, struct sched_domain parent)

		/* Flags needing groups don't count if only 1 group in parent */
		if (parent->groups == parent->groups->next)
		pflags &= ~(SD_DEGENERATE_GROUPS_MASK \| SD_PREFER_SIBLING);
		pflags &= ~SD_DEGENERATE_GROUPS_MASK;

		if (~cflags & pflags)
		return 0;

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