Messages in this thread | | | From | Kyle Meyer <> | Subject | [PATCH 0/2 RESEND] sched/topology: Optimize topology_span_sane() | Date | Tue, 9 Apr 2024 10:52:48 -0500 |
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A soft lockup is being detected in build_sched_domains() on 32 socket Sapphire Rapids systems with 3840 processors.
topology_span_sane(), called by build_sched_domains(), checks that each processor's non-NUMA scheduling domains are completely equal or completely disjoint. If a non-NUMA scheduling domain partially overlaps another, scheduling groups can break.
This series adds for_each_cpu_from() as a generic cpumask macro to optimize topology_span_sane() by removing duplicate comparisons. The total number of comparisons is reduced from N * (N - 1) to N * (N - 1) / 2 (per non-NUMA scheduling domain level), decreasing the boot time by approximately 20 seconds and preventing the soft lockup on the mentioned systems.
RESEND because Valentin Schneider reported that PATCH 2/2 wasn't delivered to all recipients.
Kyle Meyer (2): cpumask: Add for_each_cpu_from() sched/topology: Optimize topology_span_sane()
include/linux/cpumask.h | 10 ++++++++++ kernel/sched/topology.c | 6 ++---- 2 files changed, 12 insertions(+), 4 deletions(-)
-- 2.44.0
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