linux-kernel - Re: [PATCH 0/4] SLUB: calculate

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Date:   Thu, 28 Sep 2023 10:16:53 +0530
From:   Jay Patel <jaypatel@...ux.ibm.com>
To:     Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     Roman Gushchin <roman.gushchin@...ux.dev>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        patches@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] SLUB: calculate_order() cleanups

On Fri, 2023-09-08 at 16:53 +0200, Vlastimil Babka wrote:
> Since reviewing recent patches made me finally dig into these
> functions
> in details for the first time, I've also noticed some opportunities
> for
> cleanups that should make them simpler and also deliver more
> consistent
> results for some corner case object sizes (probably not seen in
> practice). Thus patch 3 can increase slab orders somewhere, but only
> in
> the way that was already intended. Otherwise it's almost no
> functional
> changes.
> 
Hi Vlastimil,

This cleanup patchset looks promising.
I've conducted test
on PowerPC with 16 CPUs and a 64K page size, and here are the results.

S
lub Memory Usage

+-------------------+--------+------------+
|                   | Normal | With Patch |
+-------------------+--------+------------+
| Total Slub Memory | 476992 | 478464     |
| Wastage           | 431    | 451        |
+-------------------+--------+------------+

Also, I have not detected any changes in the page order for slub caches
across all objects with 64K page size.

Hackbench Results

+-------+----+---------+------------+----------+
|     
  |    | Normal  | With Patch |          |
+-------+----+---------+-----
-------+----------+
| Amean | 1  | 1.1530  | 1.1347     | ( 1.59%) |
|
Amean | 4  | 3.9220  | 3.8240     | ( 2.50%) |
| Amean | 7  | 6.7943  |
6.6300     | ( 2.42%) |
| Amean | 12 | 11.7067 | 11.4423    | ( 2.26%) |
| Amean | 21 | 20.6617 | 20.1680    | ( 2.39%) |
| Amean | 30 | 29.4200
| 28.6460    | ( 2.63%) |
| Amean | 48 | 47.2797 | 46.2820    | ( 2.11%)
|
| Amean | 64 | 63.4680 | 62.1813    | ( 2.03%) |
+-------+----+------
---+------------+----------+  


Reviewed-by: Jay Patel
<jaypatel@...ux.ibm.com>
Tested-by: Jay Patel <jaypatel@...ux.ibm.com>

Th
ank You 
Jay Patel
> Vlastimil Babka (4):
>   mm/slub: simplify the last resort slab order calculation
>   mm/slub: remove min_objects loop from calculate_order()
>   mm/slub: attempt to find layouts up to 1/2 waste in
> calculate_order()
>   mm/slub: refactor calculate_order() and calc_slab_order()
> 
>  mm/slub.c | 63 ++++++++++++++++++++++++-----------------------------
> --
>  1 file changed, 27 insertions(+), 36 deletions(-)
>