linux-kernel - RE: [PATCH 2/4] mm/slab: remove slab_nomrege and slab

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Message-ID: <CO1PR11MB5185A5481010CF8B541EA7A7ECBAA@CO1PR11MB5185.namprd11.prod.outlook.com>
Date:   Wed, 22 Nov 2023 05:27:54 +0000
From:   "Song, Xiongwei" <Xiongwei.Song@...driver.com>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        "sxwjean@...com" <sxwjean@...com>
CC:     "cl@...ux.com" <cl@...ux.com>,
        "penberg@...nel.org" <penberg@...nel.org>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "roman.gushchin@...ux.dev" <roman.gushchin@...ux.dev>,
        "corbet@....net" <corbet@....net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/4] mm/slab: remove slab_nomrege and slab_merge

Hi Hyeonggon,

> -----Original Message-----
> From: owner-linux-mm@...ck.org <owner-linux-mm@...ck.org> On Behalf Of Hyeonggon
> Yoo
> Sent: Tuesday, November 21, 2023 4:44 PM
> To: sxwjean@...com
> Cc: cl@...ux.com; penberg@...nel.org; rientjes@...gle.com; iamjoonsoo.kim@....com;
> vbabka@...e.cz; roman.gushchin@...ux.dev; corbet@....net; linux-mm@...ck.org; linux-
> doc@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 2/4] mm/slab: remove slab_nomrege and slab_merge
> 
> CAUTION: This email comes from a non Wind River email account!
> Do not click links or open attachments unless you recognize the sender and know the
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> 
> On Mon, Nov 20, 2023 at 6:12 PM <sxwjean@...com> wrote:
> >
> > From: Xiongwei Song <xiongwei.song@...driver.com>
> >
> > Since slab allocatoer has already been removed, so we should also remove
> > the related parameters. And change the global flag from slab_nomerge
> > to slub_nomerge.
> 
> No, kernel parameters should be changed only in a backward-compatible
> way (if possible)
> 
> Before slab merging was supported in SLAB, only SLUB supported it.
> After commit 423c929cbbec ("mm/slab_common: commonize slab merge logic"), using
> slab_[no]merge parameters for CONFIG_SLUB builds became legal.
> 
> I think what the documentation says is "slab_[no]merge enables or
> disables slab merging
> and slub_[no]merge remain supported only for backward compatibility"

Yes. But slab allocator will not exist anymore. Is slab_[no]merge still proper? 
Will the term "slab/SLAB" still be used in the future?  

Regards,
Xiongwei
> 
> >
> > Signed-off-by: Xiongwei Song <xiongwei.song@...driver.com>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt | 11 ++---------
> >  mm/Kconfig                                      |  2 +-
> >  mm/slab_common.c                                | 13 +++++--------
> >  3 files changed, 8 insertions(+), 18 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-
> guide/kernel-parameters.txt
> > index c7709a11f8ce..afca9ff7c9f0 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -5870,11 +5870,11 @@
> >
> >         slram=          [HW,MTD]
> >
> > -       slab_merge      [MM]
> > +       slub_merge      [MM]
> >                         Enable merging of slabs with similar size when the
> >                         kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
> >
> > -       slab_nomerge    [MM]
> > +       slub_nomerge    [MM]
> >                         Disable merging of slabs with similar size. May be
> >                         necessary if there is some reason to distinguish
> >                         allocs to different slabs, especially in hardened
> > @@ -5915,13 +5915,6 @@
> >                         lower than slub_max_order.
> >                         For more information see Documentation/mm/slub.rst.
> >
> > -       slub_merge      [MM, SLUB]
> > -                       Same with slab_merge.
> > -
> > -       slub_nomerge    [MM, SLUB]
> > -                       Same with slab_nomerge. This is supported for legacy.
> > -                       See slab_nomerge for more information.
> > -
> >         smart2=         [HW]
> >                         Format: <io1>[,<io2>[,...,<io8>]]