Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751196AbXBUIq6 (ORCPT ); Wed, 21 Feb 2007 03:46:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751198AbXBUIq5 (ORCPT ); Wed, 21 Feb 2007 03:46:57 -0500 Received: from rgminet01.oracle.com ([148.87.113.118]:44400 "EHLO rgminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751196AbXBUIq4 (ORCPT ); Wed, 21 Feb 2007 03:46:56 -0500 Date: Wed, 21 Feb 2007 09:46:13 +0100 From: Jens Axboe To: Tejun Heo Cc: Robert Hancock , linux-kernel , linux-ide@vger.kernel.org, edmudama@gmail.com, Nicolas.Mailhot@LaPoste.net, Jeff Garzik , Alan Cox , Mark Lord , Ric Wheeler , Dongjun Shin , Hannes Reinecke Subject: Re: libata FUA revisited Message-ID: <20070221084613.GB3924@kernel.dk> References: <45D104F3.7040602@shaw.ca> <45D1D72D.9020509@gmail.com> <45D252CD.5010303@shaw.ca> <45D25CF2.5030508@gmail.com> <20070215180023.GA4438@kernel.dk> <45D9FE7B.60909@shaw.ca> <45DC04DF.8040002@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45DC04DF.8040002@gmail.com> X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1832 Lines: 45 On Wed, Feb 21 2007, Tejun Heo wrote: > [cc'ing Ric, Hannes and Dongjun, Hello. Feel free to drag other people in.] > > Robert Hancock wrote: > > Jens Axboe wrote: > >> But we can't really change that, since you need the cache flushed before > >> issuing the FUA write. I've been advocating for an ordered bit for > >> years, so that we could just do: > >> > >> 3. w/FUA+ORDERED > >> > >> normal operation -> barrier issued -> write barrier FUA+ORDERED > >> -> normal operation resumes > >> > >> So we don't have to serialize everything both at the block and device > >> level. I would have made FUA imply this already, but apparently it's not > >> what MS wanted FUA for, so... The current implementations take the FUA > >> bit (or WRITE FUA) as a hint to boost it to head of queue, so you are > >> almost certainly going to jump ahead of already queued writes. Which we > >> of course really do not. > > Yeah, I think if we have tagged write command and flush tagged (or > barrier tagged) things can be pretty efficient. Again, I'm much more > comfortable with separate opcodes for those rather than bits changing > the behavior. ORDERED+FUA NCQ would still be preferable to an NCQ enabled flush command, though. > Another idea Dongjun talked about while drinking in LSF was ranged > flush. Not as flexible/efficient as the previous option but much less > intrusive and should help quite a bit, I think. But that requires extensive tracking, I'm not so sure the implementation of that for barriers would be very clean. It'd probably be good for fsync, though. -- Jens Axboe - 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/