linux-kernel - [RFC 0/2] An attempt to improve SLUB on NUMA / under memory pressure

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Date:   Mon, 24 Jul 2023 04:09:04 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Roman Gushchin <roman.gushchin@...ux.dev>,
        Feng Tang <feng.tang@...el.com>,
        "Sang, Oliver" <oliver.sang@...el.com>,
        Jay Patel <jaypatel@...ux.ibm.com>,
        Binder Makin <merimus@...gle.com>, aneesh.kumar@...ux.ibm.com,
        tsahu@...ux.ibm.com, piyushs@...ux.ibm.com, fengwei.yin@...el.com,
        ying.huang@...el.com, lkp <lkp@...el.com>,
        "oe-lkp@...ts.linux.dev" <oe-lkp@...ts.linux.dev>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: [RFC 0/2] An attempt to improve SLUB on NUMA / under memory pressure

Hello folks,

This series is motivated by kernel test bot report [1] on Jay's patch
that modifies slab order. While the patch was not merged and not in the
final form, I think it was a good lesson that changing slab order has more
impacts on performance than we expected.

While inspecting the report, I found some potential points to improve
SLUB. [2] It's _potential_ because it shows no improvements on hackbench.
but I believe more realistic workloads would benefit from this. Due to
lack of resources and lack of my understanding of *realistic* workloads,
I am asking you to help evaluating this together.

It only consists of two patches. Patch #1 addresses inaccuracy in
SLUB's heuristic, which can negatively affect workloads' performance
when large folios are not available from buddy.

Patch #2 changes SLUB's behavior when there are no slabs available on the
local node's partial slab list, increasing NUMA locality when there are
available memory (without reclamation) on the local node from buddy.

This is early state, but I think it's a good enough to start discussion.
Any feedbacks and ideas are welcome. Thank you in advance!

Hyeonggon

https://lore.kernel.org/linux-mm/202307172140.3b34825a-oliver.sang@intel.com [1]
https://lore.kernel.org/linux-mm/CAB=+i9S6Ykp90+4N1kCE=hiTJTE4wzJDi8k5pBjjO_3sf0aeqg@mail.gmail.com [2]

Hyeonggon Yoo (2):
  Revert "mm, slub: change percpu partial accounting from objects to
    pages"
  mm/slub: prefer NUMA locality over slight memory saving on NUMA
    machines

 include/linux/slub_def.h |  2 --
 mm/slab.h                |  6 ++++
 mm/slub.c                | 76 ++++++++++++++++++++++++++--------------
 3 files changed, 55 insertions(+), 29 deletions(-)

-- 
2.41.0