From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id ECAC36B1DC1 for ; Mon, 19 Nov 2018 21:45:10 -0500 (EST) Received: by mail-pf1-f199.google.com with SMTP id 68so442541pfr.6 for ; Mon, 19 Nov 2018 18:45:10 -0800 (PST) Received: from mga06.intel.com (mga06.intel.com. [134.134.136.31]) by mx.google.com with ESMTPS id k27-v6si45894923pfb.216.2018.11.19.18.45.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 19 Nov 2018 18:45:09 -0800 (PST) From: "Huang\, Ying" 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> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Ming Lei Cc: Omar Sandoval , Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, linux-erofs@lists.ozlabs.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , Theodore Ts'o , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com 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