Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758499Ab2EATIy (ORCPT ); Tue, 1 May 2012 15:08:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50202 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758380Ab2EATI3 (ORCPT ); Tue, 1 May 2012 15:08:29 -0400 Date: Tue, 1 May 2012 15:08:26 -0400 From: Vivek Goyal To: Jeff Moyer Cc: Jens Axboe , Tejun Heo , Dave Jones , "linux-kernel@vger.kernel.org" , Sasha Levin Subject: Re: [PATCH v3.4-rc5] block: iocontext->nr_tasks should be initialized to one Message-ID: <20120501190826.GF18239@redhat.com> References: <1335873936.16988.148.camel@lappy> <20120501161729.GV26595@google.com> <4FA0253F.4000302@fusionio.com> <20120501180906.GX26595@google.com> <4FA028EE.7020208@fusionio.com> <20120501183610.GD18239@redhat.com> <20120501185906.GE18239@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2129 Lines: 55 On Tue, May 01, 2012 at 03:04:49PM -0400, Jeff Moyer wrote: > Vivek Goyal writes: > > > On Tue, May 01, 2012 at 02:48:41PM -0400, Jeff Moyer wrote: > >> Vivek Goyal writes: > >> > >> > On Tue, May 01, 2012 at 02:31:07PM -0400, Jeff Moyer wrote: > >> > > >> > [..] > >> >> > But as to actual users, I really don't know. I agree it's probably not > >> >> > that widely used. If google still had that code search, we could get a > >> >> > better idea :-) > >> >> > >> >> I know of one project: the venerable dump/restore utility uses CLONE_IO. > >> > > >> > I thought you wrote cooperating queue logic to fix dump as it was not > >> > using CLONE_IO and IO from multiple threads was going in separate > >> > queues. > >> > >> That's correct. I believe I sent the patch for dump before the kernel > >> patch was accepted. Plus, it can't hurt, right? > > > > Ok, so now you have fixed dump to use CLONE_IO. > > > > So only other user of coop thing remaining potentially is qemu. I was > > No, that's not the *only* other potential user. ;-) I wouldn't be > surprised if nfsd benefitted from the merging. I also wouldn't be > surprised if other 3rd party apps did. Are you trying to make a case to > get rid of the queue merging logic? No, just counting who benefits from coop logic. > > > doing some qemu testing where threads were doing IO to nearby area > > but no coop merging was taking place. So not sure in practice how well > > does it work. > > Well, that sounds like it warrants further investigation. > > > Thought, that's irrlevant for this discussion. Thought of mentioning > > this observation. > > If you can provide a reproducer, I'll be happy to take a look. I will dig. This was in the context of trying to solve qemu related IO slowdown with CFQ. Will let you know if I find a concrete reproducer. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/