Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755349AbcDJQCR (ORCPT ); Sun, 10 Apr 2016 12:02:17 -0400 Received: from casper.infradead.org ([85.118.1.10]:33444 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753506AbcDJQCQ (ORCPT ); Sun, 10 Apr 2016 12:02:16 -0400 Date: Sun, 10 Apr 2016 17:02:12 +0100 (BST) From: James Simmons To: Christoph Hellwig cc: Ming Lei , Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Boaz Harrosh , Oleg Drokin , Andreas Dilger , Greg Kroah-Hartman , "John L. Hammond" , Frank Zago , Mike Rapoport , Kent Overstreet , Julia Lawall , Al Viro , "moderated list:STAGING - LUSTRE PARALLEL FILESYSTEM" , "open list:STAGING SUBSYSTEM" Subject: Re: [PATCH 08/27] staging: lustre: avoid to use bio->bi_vcnt directly In-Reply-To: <20160410144145.GA24062@infradead.org> Message-ID: References: <1459857443-20611-1-git-send-email-tom.leiming@gmail.com> <1459857443-20611-9-git-send-email-tom.leiming@gmail.com> <20160405130109.GB32576@infradead.org> <20160410144145.GA24062@infradead.org> User-Agent: Alpine 2.20 (LFD 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160410_170212_314542_84EDEEEC X-CRM114-Status: GOOD ( 21.78 ) X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.4.0 on casper.infradead.org summary: Content analysis details: (-1.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 NO_RELAYS Informational: message was not relayed via SMTP -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1406 Lines: 28 > On Sun, Apr 10, 2016 at 03:37:42PM +0100, James Simmons wrote: > > > > > The lloop driver should be removed entirely - use the loop driver > > > instead. > > > > I talked with Andreas last week at our annual Lustre users group meeting > > about this. The reason I was told for existance is that some users were > > using files on a Lustre file system with the loop back device. The > > performance was really bad at the time so a lloop was developed to > > overcome those limitations. Its been a long time so perhaps its time > > to look at the default loop driver again to see if can perform now. If > > it doesn't we will go the route of reworking the lloop driver in the > > spirit of the cryptoloop device. > > The loop driver now supports using AIO/DIO on any file systems that > implements ->read_iter and ->write_iter. If lustre doesn't support > those or doesn't have proper performance using them it should be > addressed in the file system. > > Note that the dio mode in the loop device is not the default and you > need to manually enabled it, keep that in mind when testing. This is excellent news. The only sad thing is that most lustre users are running distros that use kernels before the AIO/DIO enhancements were landed :-( We will have to keep a copy around for those guys. But first I need to test the performance of the loop back driver this week before this can be dropped.