linux-kernel - Re: [RFC 0/2] guarantee natural alignment for kmalloc()

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Message-ID: <2b129aec-f9a5-7ab8-ca4a-0a325621d111@suse.cz>
Date:   Fri, 5 Apr 2019 19:11:17 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christopher Lameter <cl@...ux.com>
Cc:     linux-mm@...ck.org, Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Ming Lei <ming.lei@...hat.com>,
        Dave Chinner <david@...morbit.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Christoph Hellwig <hch@....de>,
        Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org
Subject: Re: [RFC 0/2] guarantee natural alignment for kmalloc()

On 3/22/19 6:52 PM, Christopher Lameter wrote:
> On Thu, 21 Mar 2019, Vlastimil Babka wrote:
> 
>> That however doesn't work well for the xfs/IO case where block sizes are
>> not known in advance:
>>
>> https://lore.kernel.org/linux-fsdevel/20190225040904.5557-1-ming.lei@redhat.com/T/#ec3a292c358d05a6b29cc4a9ce3ae6b2faf31a23f
> 
> I thought we agreed to use custom slab caches for that?

Hm maybe I missed something but my impression was that xfs/IO folks would have
to create lots of them for various sizes not known in advance, and that it
wasn't practical and would welcome if kmalloc just guaranteed the alignment.
But so far they haven't chimed in here in this thread, so I guess I'm wrong.