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[213.95.11.211]) by mx.google.com with ESMTPS id o16si16909649wrj.30.2019.04.07.01.00.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 07 Apr 2019 01:00:33 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id D0B1E68B02; Sun, 7 Apr 2019 10:00:20 +0200 (CEST) Date: Sun, 7 Apr 2019 10:00:20 +0200 From: Christoph Hellwig To: Vlastimil Babka Cc: Christopher Lameter , linux-mm@kvack.org, Pekka Enberg , David Rientjes , Joonsoo Kim , Ming Lei , Dave Chinner , Matthew Wilcox , "Darrick J . Wong" , Christoph Hellwig , Michal Hocko , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [RFC 0/2] guarantee natural alignment for kmalloc() Message-ID: <20190407080020.GA9949@lst.de> References: <20190319211108.15495-1-vbabka@suse.cz> <01000169988d4e34-b4178f68-c390-472b-b62f-a57a4f459a76-000000@email.amazonses.com> <5d7fee9c-1a80-6ac9-ac1d-b1ce05ed27a8@suse.cz> <010001699c5563f8-36c6909f-ed43-4839-82da-b5f9f21594b8-000000@email.amazonses.com> <4d2a55dc-b29f-1309-0a8e-83b057e186e6@suse.cz> <01000169a68852ed-d621a35c-af0c-4759-a8a3-e97e7dfc17a5-000000@email.amazonses.com> <2b129aec-f9a5-7ab8-ca4a-0a325621d111@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2b129aec-f9a5-7ab8-ca4a-0a325621d111@suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 05, 2019 at 07:11:17PM +0200, Vlastimil Babka wrote: > 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. Yes, in XFS we might have quite a few. Never mind all the other block level consumers that might have similar reasonable expectations but haven't triggered the problematic drivers yet.