From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f197.google.com (mail-pl1-f197.google.com [209.85.214.197]) by kanga.kvack.org (Postfix) with ESMTP id ED5E96B244F for ; Wed, 21 Nov 2018 00:35:12 -0500 (EST) Received: by mail-pl1-f197.google.com with SMTP id o10-v6so5993328plk.16 for ; Tue, 20 Nov 2018 21:35:12 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 4-v6sor55065303plh.23.2018.11.20.21.35.11 for (Google Transport Security); Tue, 20 Nov 2018 21:35:11 -0800 (PST) Subject: Re: [PATCH V10 09/19] block: introduce bio_bvecs() References: <20181115085306.9910-10-ming.lei@redhat.com> <20181116134541.GH3165@lst.de> <002fe56b-25e4-573e-c09b-bb12c3e8d25a@grimberg.me> <20181120161651.GB2629@lst.de> <53526aae-fb9b-ee38-0a01-e5899e2d4e4d@grimberg.me> <20181121005902.GA31748@ming.t460p> <2d9bee7a-f010-dcf4-1184-094101058584@grimberg.me> <20181121034415.GA8408@ming.t460p> <2a47d336-c19b-6bf4-c247-d7382871eeea@grimberg.me> <7378bf49-5a7e-5622-d4d1-808ba37ce656@grimberg.me> <20181121050359.GA31915@ming.t460p> From: Sagi Grimberg Message-ID: Date: Tue, 20 Nov 2018 21:35:07 -0800 MIME-Version: 1.0 In-Reply-To: <20181121050359.GA31915@ming.t460p> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ming Lei Cc: Christoph Hellwig , 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 , Theodore Ts'o , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com >> Wait, I see that the bvec is still a single array per bio. When you said >> a table I thought you meant a 2-dimentional array... > > I mean a new 1-d table A has to be created for multiple bios in one rq, > and build it in the following way > > rq_for_each_bvec(tmp, rq, rq_iter) > *A = tmp; > > Then you can pass A to iov_iter_bvec() & send(). > > Given it is over TCP, I guess it should be doable for you to preallocate one > 256-bvec table in one page for each request, then sets the max segment size as > (unsigned int)-1, and max segment number as 256, the preallocated table > should work anytime. 256 bvec table is really a lot to preallocate, especially when its not needed, I can easily initialize the bvec_iter on the bio bvec. If this involves preallocation of the worst-case than I don't consider this to be an improvement.