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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 01FA8C43441 for ; Tue, 20 Nov 2018 02:45:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE5B02080C for ; Tue, 20 Nov 2018 02:45:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE5B02080C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729913AbeKTNL6 (ORCPT ); Tue, 20 Nov 2018 08:11:58 -0500 Received: from mga04.intel.com ([192.55.52.120]:13768 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbeKTNL6 (ORCPT ); Tue, 20 Nov 2018 08:11:58 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2018 18:45:09 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,255,1539673200"; d="scan'208";a="109949215" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.13.27]) by orsmga002.jf.intel.com with ESMTP; 19 Nov 2018 18:45:04 -0800 From: "Huang\, Ying" To: Ming Lei Cc: Omar Sandoval , Jens Axboe , , , , Dave Chinner , Kent Overstreet , "Mike Snitzer" , , Alexander Viro , , Shaohua Li , , , David Sterba , , "Darrick J . Wong" , , Gao Xiang , "Christoph Hellwig" , Theodore Ts'o , , Coly Li , , Boaz Harrosh , "Bob Peterson" , Subject: Re: [PATCH V10 15/19] block: always define BIO_MAX_PAGES as 256 References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-16-ming.lei@redhat.com> <20181116015936.GJ23828@vader> <20181119090415.GM16736@ming.t460p> Date: Tue, 20 Nov 2018 10:45:03 +0800 In-Reply-To: <20181119090415.GM16736@ming.t460p> (Ming Lei's message of "Mon, 19 Nov 2018 17:04:16 +0800") Message-ID: <87o9ak8o28.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Ming Lei writes: > On Thu, Nov 15, 2018 at 05:59:36PM -0800, Omar Sandoval wrote: >> On Thu, Nov 15, 2018 at 04:53:02PM +0800, Ming Lei wrote: >> > Now multi-page bvec can cover CONFIG_THP_SWAP, so we don't need to >> > increase BIO_MAX_PAGES for it. >> >> You mentioned to it in the cover letter, but this needs more explanation >> in the commit message. Why did CONFIG_THP_SWAP require > 256? Why does >> multipage bvecs remove that requirement? > > CONFIG_THP_SWAP needs to split one TH page into normal pages and adds > them all to one bio. With multipage-bvec, it just takes one bvec to > hold them all. Yes. CONFIG_THP_SWAP needs to put 512 normal sub-pages into one bio to write the 512 sub-pages together. With the help of multipage-bvec, it needs just bvect to hold 512 normal sub-pages. Best Regards, Huang, Ying > thanks, > Ming