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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CB45C433F5 for ; Wed, 30 Mar 2022 01:54:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241742AbiC3Bzx (ORCPT ); Tue, 29 Mar 2022 21:55:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233672AbiC3Bzv (ORCPT ); Tue, 29 Mar 2022 21:55:51 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A314BD890; Tue, 29 Mar 2022 18:54:06 -0700 (PDT) Received: from kwepemi100021.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KSqF63yszzfYkQ; Wed, 30 Mar 2022 09:52:26 +0800 (CST) Received: from kwepemm600009.china.huawei.com (7.193.23.164) by kwepemi100021.china.huawei.com (7.221.188.223) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 30 Mar 2022 09:54:04 +0800 Received: from [10.174.176.73] (10.174.176.73) by kwepemm600009.china.huawei.com (7.193.23.164) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 30 Mar 2022 09:54:04 +0800 Subject: Re: [PATCH -next RFC 2/6] block: refactor to split bio thoroughly To: Jens Axboe , Christoph Hellwig CC: , , , , , References: <20220329094048.2107094-1-yukuai3@huawei.com> <20220329094048.2107094-3-yukuai3@huawei.com> <338207c2-e3cd-abc1-6b8c-f08645ef144a@kernel.dk> From: "yukuai (C)" Message-ID: Date: Wed, 30 Mar 2022 09:54:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <338207c2-e3cd-abc1-6b8c-f08645ef144a@kernel.dk> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.176.73] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600009.china.huawei.com (7.193.23.164) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/03/29 22:41, Jens Axboe wrote: > On 3/29/22 8:40 AM, Christoph Hellwig wrote: >> On Tue, Mar 29, 2022 at 08:35:29AM -0600, Jens Axboe wrote: >>>> But more importantly why does your use case even have splits that get >>>> submitted together? Is this a case of Linus' stupidly low default >>>> max_sectors when the hardware supports more, or is the hardware limited >>>> to a low number of sectors per request? Or do we hit another reason >>>> for the split? >>> >>> See the posted use case, it's running 512kb ios on a 128kb device. Hi, The problem was first found during kernel upgrade(v3.10 to v4.18), and we maintain a series of io performance test suites, and one of the test is fio random rw with large bs. In the environment, the 'max_sectors_kb' is 256kb, and fio bs is 1m. >> >> That is an awfully low limit these days. I'm really not sure we should >> optimize the block layer for that. > > That's exactly what my replies have been saying. I don't think this is > a relevant thing to optimize for. If the use case that large ios get submitted together is not a common issue（probably not since it's been a long time without complaining), I agree that we should not optimize the block layer for that. Thanks, Kuai > > Fixing fairness for wakeups seems useful, however. >