From: Jan Kara Subject: Re: jbd2: don't wake kjournald unnecessarily Date: Wed, 30 Jan 2013 11:41:10 +0100 Message-ID: <20130130104110.GC22091@quack.suse.cz> References: <20130121231130.GB12410@thunk.org> <20130122235041.GA7497@quack.suse.cz> <50FF3EEA.2030408@redhat.com> <20130123094421.GB9821@quack.suse.cz> <50FFFFC6.8070308@redhat.com> <20130123192911.GB21112@quack.suse.cz> <20130130052658.GE25006@thunk.org> <20130130100740.GA22091@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Theodore Ts'o , Eric Sandeen , Ext4 Developers List , mszeredi@suse.cz To: Sedat Dilek Return-path: Received: from cantor2.suse.de ([195.135.220.15]:42116 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754149Ab3A3KlY (ORCPT ); Wed, 30 Jan 2013 05:41:24 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed 30-01-13 11:29:02, Sedat Dilek wrote: > On Wed, Jan 30, 2013 at 11:07 AM, Jan Kara wrote: > > On Wed 30-01-13 00:26:58, Ted Tso wrote: > >> On Wed, Jan 23, 2013 at 08:29:11PM +0100, Jan Kara wrote: > >> > > old JBD: AIM7 jobs/min 97624.39; got 78193 jbd wakeups > >> > > new JBD: AIM7 jobs/min 85929.43; got 6306999 jbd wakeups, 6264684 extra wakeups > >> > Yeah, that's a lot. My guess would be *a lot* of processes are hanging in > >> > start_this_handle() and waiting for transaction commit. Each of them calls > >> > __log_start_commit() and things add up. Thanks for getting these numbers. > >> > >> Yeah, wow. That would imply that there are a huge number of processes > >> that get hung up in start_this_handle(), and they are waking up the > >> journal before the kjournald has a chance to set T_LOCKED (since then > >> they would get blocked earlier in start_this_handle). > >> > >> Given that, I wonder if the following change would actually help or > >> hurt things. Eric, would you be willing to ask your perf team to try > >> testing out these patches? > > Umm, I don't see anything. Forgot to attach them? > > > > Here I catched the two patches: > > http://patchwork.ozlabs.org/patch/216768/ > http://patchwork.ozlabs.org/patch/216767/ Ah, OK. Thanks for the pointer. Honza -- Jan Kara SUSE Labs, CR