From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D917C43382 for ; Tue, 25 Sep 2018 04:10:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 159362145D for ; Tue, 25 Sep 2018 04:10:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 159362145D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=acm.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727854AbeIYKQT (ORCPT ); Tue, 25 Sep 2018 06:16:19 -0400 Received: from mail-pg1-f170.google.com ([209.85.215.170]:35903 "EHLO mail-pg1-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbeIYKQT (ORCPT ); Tue, 25 Sep 2018 06:16:19 -0400 Received: by mail-pg1-f170.google.com with SMTP id d1-v6so10489638pgo.3; Mon, 24 Sep 2018 21:10:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=CBGlSRrX+tA40jmTyBQDOftMDMzSClEQD9uteDl9b5Y=; b=F2QEDEW0nR5OpKk1oWUE65gnRYOkmwmNQSj37KpsbrCRE1A9Pm14M4C0+LsVuPU2bO slg62lH6mxHP6BMCKaoDeRCH+8R0oA/+6Li3IWgGJgds4igln7PQIOOyEBjQf8MJbXIx xUxNnzHeRU9HezV9VJj1ITc7CEJCg16M1C1AHV9DCuuhNT/FbFoGnoJ6vvESRI5GBDDu uaAp7AbU8123vZvre6H14mZ9xC40snbDN6qxH8/c8sPtgUpS2HscNU5decapyjU9bE4n CEC/f4W6ZKK6VYQPMIO40nbtC5/alv4cdsGMV7Ja23l1/AtRziDXpWhsfk5qXDlM5ZGu 0jOw== X-Gm-Message-State: ABuFfohnfmUTnIFk3BoIQ8ToIKBQHN5EOEXjZsICrkdk661+ljvABMeJ 7sAfJIMEvWV/K+90zvLfF7E= X-Google-Smtp-Source: ACcGV62ueP2XpJ2SNQv9iGheAM+OWj9mk7pFJRhoa6aPiW9Nod6V2UD/MRhwOWddG54baF3WUqRk9g== X-Received: by 2002:a17:902:5ac9:: with SMTP id g9-v6mr1582815plm.311.1537848646312; Mon, 24 Sep 2018 21:10:46 -0700 (PDT) Received: from asus.site ([2601:647:4601:42b4:3842:3e31:3bb6:cf62]) by smtp.googlemail.com with ESMTPSA id w22-v6sm1036607pgm.1.2018.09.24.21.10.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 24 Sep 2018 21:10:44 -0700 (PDT) Subject: Re: block: DMA alignment of IO buffer allocated from slab To: Matthew Wilcox , Ming Lei Cc: Andrey Ryabinin , Vitaly Kuznetsov , 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 References: <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> <1537804720.195115.9.camel@acm.org> <10c706fd-2252-f11b-312e-ae0d97d9a538@virtuozzo.com> <1537805984.195115.14.camel@acm.org> <20180924185753.GA32269@bombadil.infradead.org> <20180925001615.GA14386@ming.t460p> <20180925032826.GA4110@bombadil.infradead.org> From: Bart Van Assche Message-ID: <4a19ac2f-82c1-db55-9b93-4005ace5e2fe@acm.org> Date: Mon, 24 Sep 2018 21:10:43 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20180925032826.GA4110@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/24/18 8:28 PM, Matthew Wilcox wrote: > [ ... ] Because if we have to > round all allocations below 64 bytes up to 64 bytes, [ ... ] Have you noticed that in another e-mail in this thread it has been explained why it is not necessary on x86 to align buffers allocated by kmalloc() on a 64-byte boundary even if these buffers are used for DMA? Bart.