linux-kernel - [PATCH v2 0/6] lib/group_cpus: rework grp_spread_init

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Date:   Thu,  7 Dec 2023 12:38:54 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>, Ming Lei <ming.lei@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH v2 0/6] lib/group_cpus: rework grp_spread_init_one() and make it O(1)

grp_spread_init_one() implementation is sub-optimal because it
traverses bitmaps from the beginning, instead of picking from the
previous iteration.

Fix it and use find_bit API where appropriate. While here, optimize
cpumasks allocation and drop unneeded cpumask_empty() call.

---
v1: https://lore.kernel.org/all/ZW5MI3rKQueLM0Bz@yury-ThinkPad/T/
v2: add few more optimizations (patches 5-6)

Yury Norov (6):
  cpumask: introduce for_each_cpu_and_from()
  lib/group_cpus: relax atomicity requirement in grp_spread_init_one()
  lib/group_cpus: optimize inner loop in grp_spread_init_one()
  lib/group_cpus: optimize outer loop in grp_spread_init_one()
  lib/cgroup_cpus.c: don't zero cpumasks in group_cpus_evenly() on
    allocation
  lib/group_cpus.c: drop unneeded cpumask_empty() call in
    __group_cpus_evenly()

 include/linux/cpumask.h | 11 ++++++++++
 include/linux/find.h    |  3 +++
 lib/group_cpus.c        | 47 +++++++++++++++++++----------------------
 3 files changed, 36 insertions(+), 25 deletions(-)

-- 
2.40.1