From: Kyle Meyer <kyle.meyer@hpe.com>
To: linux-kernel@vger.kernel.org, yury.norov@gmail.com,
andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk,
mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vschneid@redhat.com
Cc: russ.anderson@hpe.com, dimitri.sivanich@hpe.com,
steve.wahl@hpe.com, Kyle Meyer <kyle.meyer@hpe.com>
Subject: [PATCH v2 0/2] sched/topology: Optimize topology_span_sane()
Date: Wed, 10 Apr 2024 16:33:09 -0500 [thread overview]
Message-ID: <20240410213311.511470-1-kyle.meyer@hpe.com> (raw)
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
next reply other threads:[~2024-04-10 21:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 21:33 Kyle Meyer [this message]
2024-04-10 21:33 ` [PATCH v2 1/2] cpumask: Add for_each_cpu_from() Kyle Meyer
2024-04-15 11:50 ` Valentin Schneider
2024-04-10 21:33 ` [PATCH v2 2/2] sched/topology: Optimize topology_span_sane() Kyle Meyer
2024-04-11 10:38 ` Andy Shevchenko
2024-04-11 21:55 ` Kyle Meyer
2024-04-12 14:25 ` Andy Shevchenko
2024-04-13 17:42 ` Yury Norov
2024-04-15 11:50 ` Valentin Schneider
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