From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC fs] v2 Make sync() satisfy many requests with one invocation Date: Tue, 30 Jul 2013 10:43:36 -0700 Message-ID: <20130730174336.GD26694@linux.vnet.ibm.com> References: <20130726232852.GA15147@linux.vnet.ibm.com> <20130727025703.GF21982@dastard> <20130727040524.GC26694@linux.vnet.ibm.com> <20130727062101.GG21982@dastard> <20130727112628.GE26694@linux.vnet.ibm.com> <20130729070643.GH21982@dastard> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davej@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, hch@lst.de, jack@suse.cz, curtw@google.com, jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org To: Dave Chinner Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:47567 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752800Ab3G3RrG (ORCPT ); Tue, 30 Jul 2013 13:47:06 -0400 Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 30 Jul 2013 11:47:05 -0600 Content-Disposition: inline In-Reply-To: <20130729070643.GH21982@dastard> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Jul 29, 2013 at 05:06:43PM +1000, Dave Chinner wrote: > On Sat, Jul 27, 2013 at 04:26:28AM -0700, Paul E. McKenney wrote: > > On Sat, Jul 27, 2013 at 04:21:01PM +1000, Dave Chinner wrote: > > > On Fri, Jul 26, 2013 at 09:05:24PM -0700, Paul E. McKenney wrote: > > > > Could you please send your patches over to Dave Jones right now? I am > > > > getting quite tired of getting RCU CPU stall warning complaints from > > > > him that turn out to be due to highly contended sync() system calls. > > > > > > Then ignore them until the code is ready - it'll be 3.12 before the > > > fixes are merged, anyway, because the lock contention fix requires > > > infrastructure that is currently in mmotm that is queued for 3.12 > > > (i.e. the per-node list infrastructure) to fix a whole bunch of > > > other, more critical VFS lock contention problems. Seeing as a new > > > mmotm went out last week, I should have the patches ready for review > > > early next week. > > > > > > FWIW, we (as in XFS filesystem testers) regularly run tests that > > > have hundreds of concurrent sys_sync() calls running at the same > > > time. e.g. xfstests::xfs/297 runs a 1000 fsstress processes while > > > freezing and unfreezing the filesystem, and that usually shows > > > hundreds of threads running sys_sync concurrently after a short > > > amount of runtime. So it's pretty clear that what Dave is seeing > > > is not necessarily representative of what happens when there ar lots > > > of sys_sync() calls run concurrently. > > > > So Dave might be finding an additional problem. ;-) > > Dave will always find problems. If you want something broken, give > it to Dave and he'll hand it back in pieces. :) So rather than Wreck-it Ralph, we have Destroy-it Dave? ;-) And I must hasten to add that Dave's destroy-it services, though sometimes irritating, are almost always quite valuable. > > > BTW, concurrent syncfs() calls are going to have exactly the same > > > problem as concurrent sync() calls, as is any other operation that > > > results in a walk of the per-superblock inodes list. > > > > Yep! Your upcoming patch addresses these as well? > > Yes, it does. Good to hear, looking forward to seeing them? Thanx, Paul