linux-kernel - Re: [PATCH] mm/slub: replace alloc_pages with folio

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Message-ID: <YpLhSokkrPrXjNXP@FVFYT0MHHV2J.googleapis.com>
Date:   Sun, 29 May 2022 10:58:18 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     bh1scw@...il.com, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: replace alloc_pages with folio_alloc

On Sat, May 28, 2022 at 05:27:11PM +0100, Matthew Wilcox wrote:
> On Sun, May 29, 2022 at 12:11:58AM +0800, bh1scw@...il.com wrote:
> > From: Fanjun Kong <bh1scw@...il.com>
> > 
> > This patch will use folio allocation functions for allocating pages.
> 
> That's not actually a good idea.  folio_alloc() will do the
> prep_transhuge_page() step which isn't needed for slab.
>

You mean folio_alloc() is dedicated for THP allocation?  It is a little
surprise to me.  I thought folio_alloc() is just a variant of alloc_page(),
which returns a folio struct instead of a page.  Seems like I was wrong.
May I ask what made us decide to do this?

Thanks.