linux-kernel - [PATCH v4 0/9] lib/group_cpus: rework grp_spread_init

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Date: Thu, 28 Dec 2023 12:09:27 -0800
From: Yury Norov <yury.norov@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ming Lei <ming.lei@...hat.com>,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH v4 0/9] lib/group_cpus: rework grp_spread_init_one() and make it O(1)

Hi Andrew, Ming,

Now that we've got a couple more weeks, let's try to merge this series in
the upcoming merge window? In addition to addressing the v3 comments, in
v4 I added a few more patches that simplify the code for more by using
cleanup machinery.

Thanks,
	Yury
--

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: https://lore.kernel.org/lkml/ZXKNVRu3AfvjaFhK@fedora/T/
v3: https://lore.kernel.org/all/ZYnD4Bp8R9oIz19s@yury-ThinkPad/T/
v4:
 - drop patch v3 #7 and add a comment in patch #4;
 - patch #2: fix cpus_per_grp decrement order;
 - patch #3: add NAK fro Ming Lei;
 - add patches #7-9 that simplify the code for more.

Yury Norov (9):
  cpumask: introduce for_each_cpu_and_from()
  lib/group_cpus: optimize inner loop in grp_spread_init_one()
  lib/group_cpus: relax atomicity requirement in grp_spread_init_one()
  lib/group_cpus: optimize outer loop in grp_spread_init_one()
  lib/group_cpus: don't zero cpumasks in group_cpus_evenly() on
    allocation
  lib/group_cpus: drop unneeded cpumask_empty() call in
    __group_cpus_evenly()
  cpumask: define cleanup function for cpumasks
  lib/group_cpus: rework group_cpus_evenly()
  lib/group_cpus: simplify group_cpus_evenly() for more

 include/linux/cpumask.h |  14 ++++++
 include/linux/find.h    |   3 ++
 lib/group_cpus.c        | 104 +++++++++++++++++-----------------------
 3 files changed, 62 insertions(+), 59 deletions(-)

-- 
2.40.1