Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754766Ab0GTTcg (ORCPT ); Tue, 20 Jul 2010 15:32:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57431 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751150Ab0GTTcd (ORCPT ); Tue, 20 Jul 2010 15:32:33 -0400 Date: Tue, 20 Jul 2010 15:32:24 -0400 From: Vivek Goyal To: Corrado Zoccolo Cc: Christoph Hellwig , Jeff Moyer , axboe@kernel.dk, Linux-Kernel Subject: Re: [PATCH 0/2] cfq-iosched: fixing RQ_NOIDLE handling. Message-ID: <20100720193224.GM8967@redhat.com> References: <20100713195650.GA21044@redhat.com> <20100713204236.GB21044@redhat.com> <20100720141102.GA6316@infradead.org> <20100720142647.GA8967@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2060 Lines: 38 On Tue, Jul 20, 2010 at 09:10:56PM +0200, Corrado Zoccolo wrote: > On Tue, Jul 20, 2010 at 4:26 PM, Vivek Goyal wrote: > > On Tue, Jul 20, 2010 at 10:11:03AM -0400, Christoph Hellwig wrote: > >> Didn't you guys have a previous iteration of the fixes that gets > >> rid of REQ_NODILE by improving the heuristics inside cfq? ?That > >> would be much, much preffered from the filesystem point of view. > I think the previous iteration required more complex heuristics, while > this one uses existing ones to handle one more class of problems. > I understand that you still see the complexity from the fs side, but > Vivek's proposal may help also there. It only needs to be tested thoroughly. > > > > > Actually in this patch, I was thinking we can probably get rid of > > RQ_NOIDLE flag and just check for WRITE_SYNC. Any WRITE_SYNC queue > > gets served on sync-noidle tree. I am wondering will we not face jbd > > thread issues with direct writes also? If yes, then not special casing > > direct IO writes and treat them same as O_SYNC writes will make sense. > > Probably it is better to submit this first, since it is already > tested, and then have a different patch that can finish the work > This will help when bisecting for possible regressions, since I'm not > sure why the other writes are not already marked with RQ_NOIDLE (maybe > it was introduced for some good reason to distinguish the two sets, > and we won't know unless we find the workload where it helped). > I'll resend the current patch with Jeff's reviewed and tested tags. > I am fine with pushing this patch as it is first and then once we have an answer to question whether direct IO path and O_SYNC/fsync path need same treatment or different treatment in IO scheduler, we can fix RQ_NOIDLE flag issue also. 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/