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([2620:15c:2cd:203:5cdc:422c:7b28:ebb5]) by smtp.gmail.com with ESMTPSA id w12-v6sm55026294pfd.110.2018.09.24.08.58.41 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 24 Sep 2018 08:58:42 -0700 (PDT) Message-ID: <1537804720.195115.9.camel@acm.org> Subject: Re: block: DMA alignment of IO buffer allocated from slab From: Bart Van Assche To: Andrey Ryabinin , Ming Lei , Vitaly Kuznetsov Cc: Christoph Hellwig , Ming Lei , linux-block , linux-mm , Linux FS Devel , "open list:XFS FILESYSTEM" , Dave Chinner , Linux Kernel Mailing List , Jens Axboe , Christoph Lameter , Linus Torvalds , Greg Kroah-Hartman Date: Mon, 24 Sep 2018 08:58:40 -0700 In-Reply-To: References: <20180920063129.GB12913@lst.de> <87h8ij0zot.fsf@vitty.brq.redhat.com> <20180923224206.GA13618@ming.t460p> <38c03920-0fd0-0a39-2a6e-70cd8cb4ef34@virtuozzo.com> <20a20568-5089-541d-3cee-546e549a0bc8@acm.org> <12eee877-affa-c822-c9d5-fda3aa0a50da@virtuozzo.com> <1537801706.195115.7.camel@acm.org> Content-Type: text/plain; charset="UTF-7" X-Mailer: Evolution 3.26.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2018-09-24 at 18:52 +-0300, Andrey Ryabinin wrote: +AD4 Yes, with CONFIG+AF8-DEBUG+AF8-SLAB+AD0-y, CONFIG+AF8-SLUB+AF8-DEBUG+AF8-ON+AD0-y kmalloc() guarantees +AD4 that result is aligned on ARCH+AF8-KMALLOC+AF8-MINALIGN boundary. Had you noticed that Vitaly Kuznetsov showed that this is not the case? See also https://lore.kernel.org/lkml/87h8ij0zot.fsf+AEA-vitty.brq.redhat.com/. Thanks, Bart.