From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753583Ab1AYKVk (ORCPT ); Tue, 25 Jan 2011 05:21:40 -0500 Received: from mail-fx0-f46.google.com ([209.85.161.46]:36596 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753450Ab1AYKVg (ORCPT ); Tue, 25 Jan 2011 05:21:36 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=gYBm9JQXEtql7j1tE4ydlQNohGfc5PlD1AN4Tz+VKjtMHxZQD1trK/lQ65ARtneJBL CNNcRhWr1Vub/CKYkfUmOQ2GFKXVoJ6Rl2TTC1KKabhJfd8iq4LQrgxeqAfrV1UmvD2J hbavQJy9P+jgX3tUxKlu5gvEnwZWZ/8HaNvtI= Date: Tue, 25 Jan 2011 11:21:28 +0100 From: Tejun Heo To: "Darrick J. Wong" Cc: Vivek Goyal , axboe@kernel.dk, tytso@mit.edu, shli@kernel.org, neilb@suse.de, adilger.kernel@dilger.ca, jack@suse.cz, snitzer@redhat.com, linux-kernel@vger.kernel.org, kmannth@us.ibm.com, cmm@us.ibm.com, linux-ext4@vger.kernel.org, rwheeler@redhat.com, hch@lst.de, josef@redhat.com Subject: Re: [PATCH 3/3] block: reimplement FLUSH/FUA to support merge Message-ID: <20110125102128.GO27510@htj.dyndns.org> References: <1295625598-15203-1-git-send-email-tj@kernel.org> <1295625598-15203-4-git-send-email-tj@kernel.org> <20110121185617.GI12072@redhat.com> <20110123102526.GA23121@htj.dyndns.org> <20110124203155.GA32261@tux1.beaverton.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110124203155.GA32261@tux1.beaverton.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Darrick. On Mon, Jan 24, 2011 at 12:31:55PM -0800, Darrick J. Wong wrote: > > So, I think it's better to start with something simple and improve it > > with actual testing. If the current simple implementation can match > > Darrick's previous numbers, let's first settle the mechanisms. We can > > Yep, the fsync-happy numbers more or less match... at least for 2.6.37: > http://tinyurl.com/4q2xeao Good to hear. Thanks for the detailed testing. > I'll give 2.6.38-rc2 a try later, though -rc1 didn't boot for me, so these > numbers are based on a backport to .37. :( Well, there hasn' been any change in the area during the merge window anyway, so I think testing on 2.6.37 should be fine. > > I don't really think we should design the whole thing around broken > > devices which incorrectly report writeback cache when it need not. > > The correct place to work around that is during device identification > > not in the flush logic. > > elm3a4_sas and elm3c71_extsas advertise writeback cache yet the > flush completion times are suspiciously low. I suppose it could be > useful to disable flushes to squeeze out that last bit of > performance, though I don't know how one goes about querying the > disk array to learn if there's a battery behind the cache. I guess > the current mechanism (admin knob that picks a safe default) is good > enough. Yeap, that or a blacklist of devices which lie. Jens, what do you think? If you don't object, let's put this through linux-next. Thank you. -- tejun