From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752522AbbIQPTP (ORCPT ); Thu, 17 Sep 2015 11:19:15 -0400 Received: from mail-io0-f170.google.com ([209.85.223.170]:35517 "EHLO mail-io0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751778AbbIQPTN (ORCPT ); Thu, 17 Sep 2015 11:19:13 -0400 Subject: Re: [PATCH] block: blk-merge: fast-clone bio when splitting rw bios To: Ming Lei , linux-kernel@vger.kernel.org References: <1442502807-24377-1-git-send-email-ming.lei@canonical.com> Cc: Christoph Hellwig , Kent Overstreet , Ming Lin , Dongsu Park From: Jens Axboe Message-ID: <55FAD9EF.5040100@kernel.dk> Date: Thu, 17 Sep 2015 09:19:11 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <1442502807-24377-1-git-send-email-ming.lei@canonical.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/17/2015 09:13 AM, Ming Lei wrote: > biovecs has become immutable since v3.13, so it isn't necessary > to allocate biovecs for the new cloned bios, then we can save > one extra biovecs allocation/copy, and the allocation is often > not fixed-length and a bit more expensive. > > For example, if the 'max_sectors_kb' of null blk's queue is set > as 16(32 sectors) via sysfs just for making more splits, this patch > can increase throught about ~70% in the sequential read test over > null_blk(direct io, bs: 1M). I'd be curious how this compares to before we did the splitting, not exceeding the limits through bio_add_page() instead? -- Jens Axboe