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[195.135.220.15]) by mx.google.com with ESMTPS id m4si2586752edr.313.2019.04.09.01.07.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Apr 2019 01:07:44 -0700 (PDT) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DAE55AC97; Tue, 9 Apr 2019 08:07:43 +0000 (UTC) Subject: Re: [RFC 0/2] guarantee natural alignment for kmalloc() To: Christoph Hellwig Cc: Christopher Lameter , linux-mm@kvack.org, Pekka Enberg , David Rientjes , Joonsoo Kim , Ming Lei , Dave Chinner , Matthew Wilcox , "Darrick J . Wong" , Michal Hocko , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, lsf-pc@lists.linux-foundation.org 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> <20190407080020.GA9949@lst.de> From: Vlastimil Babka Message-ID: Date: Tue, 9 Apr 2019 10:07:42 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190407080020.GA9949@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 4/7/19 10:00 AM, Christoph Hellwig wrote: > 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. What about a LSF session/BoF to sort this out, then? Would need to have people from all three MM+FS+IO groups, I suppose.