Messages in this thread | | | From | Kyle Meyer <> | Subject | [PATCH v2 0/2] sched/topology: Optimize topology_span_sane() | Date | Wed, 10 Apr 2024 16:33:09 -0500 |
| |
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 on each non-NUMA scheduling domain level, decreasing the boot time by approximately 20 seconds and preventing the soft lockup on the mentioned systems.
Changes in v2: * 1/2: Change for_each_cpu()'s description. * 2/2: Add more information to the commit message. * https://lore.kernel.org/linux-kernel/20240409155250.3660517-1-kyle.meyer@hpe.com/T/
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
| |