From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932181AbbFINtj (ORCPT ); Tue, 9 Jun 2015 09:49:39 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:34651 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752506AbbFINtd (ORCPT ); Tue, 9 Jun 2015 09:49:33 -0400 From: Ming Lei To: linux-kernel@vger.kernel.org, Dave Kleikamp Cc: Jens Axboe , Zach Brown , Christoph Hellwig , Maxim Patlasov , Andrew Morton , Alexander Viro , Tejun Heo , Dave Chinner Subject: [PATCH v5 0/5] block: loop: improve loop with AIO Date: Tue, 9 Jun 2015 21:49:21 +0800 Message-Id: <1433857766-6153-1-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Guys, There are about 3 advantages to use direct I/O and AIO on read/write loop's backing file: 1) double cache can be avoided, then memory usage gets decreased a lot 2) not like user space direct I/O, there isn't cost of pinning pages 3) avoid context switch for obtaining good throughput - in buffered file read, random I/O throughput is often obtained only if they are submitted concurrently from lots of tasks; but for sequential I/O, most of times they can be hit from page cache, so concurrent submissions often introduce unnecessary context switch and can't improve throughput much. There was such discussion[1] to use non-blocking I/O to improve the problem for application. - with direct I/O and AIO, concurrent submissions can be avoided and random read throughput can't be affected meantime So this patchset trys to improve loop via AIO, and about 45% memory usage can be decreased, see detailed data in commit log of patch4, also IO throughput isn't affected too. V5: - don't introduce IOCB_DONT_DIRTY_PAGE and bypass dirtying for ITER_KVEC and ITER_BVEC direct IO(read), as required by Christoph V4: - add detailed commit log for 'use kthread_work' - allow userspace(sysfs, losetup) to decide if dio/aio is used as suggested by Christoph and Dave Chinner - only use dio if the backing block device's min io size is 512 as pointed by Dave Chinner & Christoph V3: - based on Al's iov_iter work and Christoph's kiocb changes - use kthread_work - introduce IOCB_DONT_DIRTY_PAGE flag - set QUEUE_FLAG_NOMERGES for loop's request queue V2: - remove 'extra' parameter to aio_kernel_alloc() - try to avoid memory allcation inside queue req callback - introduce 'use_mq' sysfs file for enabling kernel aio or disabling it V1: - link: http://marc.info/?t=140803157700004&r=1&w=2 - improve failure path in aio_kernel_submit() drivers/block/loop.c | 229 ++++++++++++++++++++++++++++++++++++++++++++++++++---------------- drivers/block/loop.h | 13 ++-- fs/direct-io.c | 9 ++- 3 files changed, 186 insertions(+), 65 deletions(-) Thanks, Ming