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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 AD8D2C433DF for ; Tue, 16 Jun 2020 04:16:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83C9F207E8 for ; Tue, 16 Jun 2020 04:16:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Sv8NB9se" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725562AbgFPEQi (ORCPT ); Tue, 16 Jun 2020 00:16:38 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:45433 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725306AbgFPEQi (ORCPT ); Tue, 16 Jun 2020 00:16:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592280997; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O1xnRnGhMhEwz+wjNoiBLED8iGeKhij45TdHR9vNevI=; b=Sv8NB9seoKSHuH/D6DWfs4L9k3f9f6jswFqIFJmtVU8ZdFHEMQ+K0hwcCxtWmiFnbdt4Fm EZD5ZoGhGw8a8OxE5pGqxE0Hr2V82vPPPxxWZr4GMXW0XrtGn9xvv9WJKa1hLtXLJlmOAx uwo2y+oZMc8WKLnA/zdKyftCjYxOp2k= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-43-dxsaplCfNMSfSVigeg3-jg-1; Tue, 16 Jun 2020 00:16:34 -0400 X-MC-Unique: dxsaplCfNMSfSVigeg3-jg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E9FA5188361B; Tue, 16 Jun 2020 04:16:33 +0000 (UTC) Received: from T590 (ovpn-12-136.pek2.redhat.com [10.72.12.136]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C9E7160C05; Tue, 16 Jun 2020 04:16:28 +0000 (UTC) Date: Tue, 16 Jun 2020 12:16:24 +0800 From: Ming Lei To: harshad shirwadkar Cc: linux-block@vger.kernel.org, "Theodore Y. Ts'o" Subject: Re: [PATCH] block: add split_alignment for request queue Message-ID: <20200616041624.GA52855@T590> References: <20200616005633.172804-1-harshadshirwadkar@gmail.com> <20200616024028.GE27192@T590> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Jun 15, 2020 at 08:24:08PM -0700, harshad shirwadkar wrote: > After taking a closer look, I don't see chunk_sectors being accounted > for in the splitting code. If I understand correctly, the implementation > of chunk_sectors is such that it allows for one big IO to go through. > In other words, it tries to avoid the splitting code if possible. But, > it doesn't seem to guarantee that when an IO is split, it will be Please take a look at blk_max_size_offset() which is called by get_max_io_size() from blk_bio_segment_split(), which splits bio into chunk_sectors aligned bio. Also you may run IO trace on queue with chunk_sectors setup, and check if the splitted IO request is what you expected. Thanks, Ming