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Wed, 10 Apr 2024 21:43:12 +0000 Received: from p1lg14885.dc01.its.hpecorp.net (unknown [10.119.18.236]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by p1lg14878.it.hpe.com (Postfix) with ESMTPS id 7030F1317A; Wed, 10 Apr 2024 21:43:11 +0000 (UTC) Received: from dog.eag.rdlabs.hpecorp.net (unknown [16.231.227.36]) by p1lg14885.dc01.its.hpecorp.net (Postfix) with ESMTP id BFD8E80047C; Wed, 10 Apr 2024 21:43:10 +0000 (UTC) Received: by dog.eag.rdlabs.hpecorp.net (Postfix, from userid 48777) id 4AD72302F4723; Wed, 10 Apr 2024 16:33:19 -0500 (CDT) From: Kyle Meyer 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 Subject: [PATCH v2 0/2] sched/topology: Optimize topology_span_sane() Date: Wed, 10 Apr 2024 16:33:09 -0500 Message-Id: <20240410213311.511470-1-kyle.meyer@hpe.com> X-Mailer: git-send-email 2.26.2 X-Proofpoint-ORIG-GUID: UoHMcuuEjPBEIrT-Rm-IdZ63igZGdgbJ X-Proofpoint-GUID: UoHMcuuEjPBEIrT-Rm-IdZ63igZGdgbJ Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-04-10_06,2024-04-09_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 impostorscore=0 clxscore=1015 adultscore=0 mlxlogscore=521 lowpriorityscore=0 mlxscore=0 spamscore=0 bulkscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000 definitions=main-2404100159 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