From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vivek Goyal Subject: Re: 2.6.35-rc2-git2: Reported regressions from 2.6.34 Date: Fri, 11 Jun 2010 15:48:49 -0400 Message-ID: <20100611194849.GB20837@redhat.com> References: <4C0F4872.7090909@fusionio.com> <20100611083249.GA11143@elte.hu> <4C11F661.3070604@fusionio.com> <20100611085520.GA20218@elte.hu> <4C11FF77.1000101@fusionio.com> <20100611190714.GA20837@redhat.com> <4C128A75.3030501@fusionio.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <4C128A75.3030501-5c4llco8/ftWk0Htik3J/w@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jens Axboe Cc: Ingo Molnar , Linus Torvalds , "Rafael J. Wysocki" , Carl Worth , Eric Anholt , Divyesh Shah , "guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org" , Linux Kernel Mailing List , Andrew Morton , Kernel Testers List On Fri, Jun 11, 2010 at 09:11:49PM +0200, Jens Axboe wrote: > On 11/06/10 21.07, Vivek Goyal wrote: > > On Fri, Jun 11, 2010 at 11:18:47AM +0200, Jens Axboe wrote: > >> On 2010-06-11 10:55, Ingo Molnar wrote: > >>>>> Caused by the same blkiocg_update_io_add_stats() function. Bootlog and config > >>>>> attached. Reproducible on that sha1 and with that config. > >>>> > >>>> I think I see it, the internal CFQ blkg groups are not properly > >>>> initialized... Will send a patch shortly. > >>> > >>> Cool - can test it with a short turnaround, the bug is easy to reproduce. > >> > >> Here's a nasty patch that should fix it. Not optimal, since we really > >> just want empty functions for these when cfq group scheduling is not > >> defined. > >> > >> CC'ing the guilty parties to come up with a better patch that does NOT > >> involve ifdefs in cfq-iosched.c. We want blk-cgroup.[ch] fixed up. > >> And trimming the CC list a bit. > > > > Jens, Ingo, I am sorry for this mess. > > > > Jens, > > > > How about introducing "block/cfq.h" and declaring additional set of wrapper > > functions to update blkiocg stats and make these do nothing if > > CFQ_GROUP_IOSCHED=n. > > > > For example, in linux-2.6/block/cfq.h, we can define functions as follows. > > > > #ifdef CONFIG_CFQ_GROUP_IOSCHED > > cfq_blkiocg_update_dequeue_stats () { > > blkiocg_update_dequeue_stats() > > } > > #else > > cfq_blkiocg_update_dequeue_stats () {} > > #endif > > > > Fixing it blk-cgroup.[ch] might not be best as BLK_CGROUP is set. > > Secondly, if there are other IO control policies later, they might > > want to make use of BLK_CGROUP while cfq has disabled the group io > > scheduling. > > I already tried such a patch, but it's not exactly pretty. How about > splitting blk-cgroup.c into two parts, one that is built for > BLK_CGROUP and an additional one that is also built for > CFQ_GROUP_SCHED? Lets try and improve on the ifdef mess, not extend > it. Sorry, I did not understand your suggestion. Can you please throw some more light on it. blk-cgroup.c does not have any cfq specific parts. So I can't split it out and build part of it based on CFQ_GROUP_SCHED. Thanks Vivek