From owner-freebsd-stable@FreeBSD.ORG Fri Jun 22 14:24:24 2012 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 601BF1065674 for ; Fri, 22 Jun 2012 14:24:24 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id 225048FC0A for ; Fri, 22 Jun 2012 14:24:24 +0000 (UTC) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 71A67B9B3; Fri, 22 Jun 2012 10:24:23 -0400 (EDT) From: John Baldwin To: Charles Owens Date: Fri, 22 Jun 2012 10:22:57 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p13; KDE/4.5.5; amd64; ; ) References: <4FDABA0B.5030702@greatbaysoftware.com> <201206150804.46341.jhb@freebsd.org> <4FE3DA14.9090506@greatbaysoftware.com> In-Reply-To: <4FE3DA14.9090506@greatbaysoftware.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201206221022.57632.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Fri, 22 Jun 2012 10:24:23 -0400 (EDT) Cc: freebsd-stable@freebsd.org Subject: Re: mfi(4) IO performance regression, post 8.1 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Jun 2012 14:24:24 -0000 On Thursday, June 21, 2012 10:36:04 pm Charles Owens wrote: > > On 6/15/12 8:04 AM, John Baldwin wrote: > > On Friday, June 15, 2012 12:28:59 am Charles Owens wrote: > >> Hello FreeBSD folk, > >> > >> We're seeing what appears to be a storage performance regression as we > >> try to move from 8.1 (i386) to 8.3. We looked at 8.2 also and it > >> appears that the regression happened between 8.1 and 8.2. > >> > >> Our system is an Intel S5520UR Server with 12 GB RAM, dual 4-core CPUs. > >> Storage is a LSI MegaSAS 1078 controller (mfi) in a RAID-10 > >> configuration, using UFS + geom_journal for filesystem. > >> > >> Postgresql performance, as seen via pgbench, dropped by approx 20%. > >> This testing was done with our usual PAE-enabled kernels. We then went > >> back to GENERIC kernels and did comparisons using "bonnie", results > >> below. Following that is a kernel boot log. > >> > >> Notably, we're seeing this regression only with our RAID mfi(4) based > >> systems. Notably, from looking at FreeBSD source changelogs it appears > >> that the mfi(4) code has seen some changes since 8.1. > > Between 8.1 and 8.2 mfi has not had any significant changes. The only changes > > made to sys/dev/mfi were to add a new constant: > > > >> svn diff svn+ssh://svn.freebsd.org/base/releng/8.1/sys/dev/mfi > > svn+ssh://svn.freebsd.org/base/releng/8.2/sys/dev/mfi > > Index: mfireg.h > > =================================================================== > > --- mfireg.h (.../8.1/sys/dev/mfi) (revision 237134) > > +++ mfireg.h (.../8.2/sys/dev/mfi) (revision 237134) > > @@ -975,7 +975,9 @@ > > MFI_PD_STATE_OFFLINE = 0x10, > > MFI_PD_STATE_FAILED = 0x11, > > MFI_PD_STATE_REBUILD = 0x14, > > - MFI_PD_STATE_ONLINE = 0x18 > > + MFI_PD_STATE_ONLINE = 0x18, > > + MFI_PD_STATE_COPYBACK = 0x20, > > + MFI_PD_STATE_SYSTEM = 0x40 > > }; > > > > union mfi_ld_ref { > > > > The difference in write performance must be due to something else. You > > mentioned you are using UFS + gjournal. I think gjournal uses BIO_FLUSH, so I > > wonder if this is related: > > > > ------------------------------------------------------------------------ > > r212939 | gibbs | 2010-09-20 19:39:00 -0400 (Mon, 20 Sep 2010) | 61 lines > > > > MFC 212160: > > > > Correct bioq_disksort so that bioq_insert_tail() offers barrier semantic. > > Add the BIO_ORDERED flag for struct bio and update bio clients to use it. > > > > The barrier semantics of bioq_insert_tail() were broken in two ways: > > > > o In bioq_disksort(), an added bio could be inserted at the head of > > the queue, even when a barrier was present, if the sort key for > > the new entry was less than that of the last queued barrier bio. > > > > o The last_offset used to generate the sort key for newly queued bios > > did not stay at the position of the barrier until either the > > barrier was de-queued, or a new barrier (which updates last_offset) > > was queued. When a barrier is in effect, we know that the disk > > will pass through the barrier position just before the > > "blocked bios" are released, so using the barrier's offset for > > last_offset is the optimal choice. > > > > sys/geom/sched/subr_disk.c: > > sys/kern/subr_disk.c: > > o Update last_offset in bioq_insert_tail(). > > > > o Only update last_offset in bioq_remove() if the removed bio is > > at the head of the queue (typically due to a call via > > bioq_takefirst()) and no barrier is active. > > > > o In bioq_disksort(), if we have a barrier (insert_point is non-NULL), > > set prev to the barrier and cur to it's next element. Now that > > last_offset is kept at the barrier position, this change isn't > > strictly necessary, but since we have to take a decision branch > > anyway, it does avoid one, no-op, loop iteration in the while > > loop that immediately follows. > > > > o In bioq_disksort(), bypass the normal sort for bios with the > > BIO_ORDERED attribute and instead insert them into the queue > > with bioq_insert_tail(). bioq_insert_tail() not only gives > > the desired command order during insertion, but also provides > > barrier semantics so that commands disksorted in the future > > cannot pass the just enqueued transaction. > > > > sys/sys/bio.h: > > Add BIO_ORDERED as bit 4 of the bio_flags field in struct bio. > > > > sys/cam/ata/ata_da.c: > > sys/cam/scsi/scsi_da.c > > Use an ordered command for SCSI/ATA-NCQ commands issued in > > response to bios with the BIO_ORDERED flag set. > > > > sys/cam/scsi/scsi_da.c > > Use an ordered tag when issuing a synchronize cache command. > > > > Wrap some lines to 80 columns. > > > > sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c > > sys/geom/geom_io.c > > Mark bios with the BIO_FLUSH command as BIO_ORDERED. > > > > Sponsored by: Spectra Logic Corporation > > ------------------------------------------------------------------------ > > > > Can you try perhaps commenting out the 'bp->bio_flags |= BIO_ORDERED' line > > changed in geom_io.c in 8.2? That would be effectively reverting this > > portion of the diff: > > > > Index: geom_io.c > > =================================================================== > > --- geom_io.c (.../8.1/sys/geom) (revision 237134) > > +++ geom_io.c (.../8.2/sys/geom) (revision 237134) > > @@ -265,6 +265,7 @@ > > g_trace(G_T_BIO, "bio_flush(%s)", cp->provider->name); > > bp = g_alloc_bio(); > > bp->bio_cmd = BIO_FLUSH; > > + bp->bio_flags |= BIO_ORDERED; > > bp->bio_done = NULL; > > bp->bio_attribute = NULL; > > bp->bio_offset = cp->provider->mediasize; > > > > John... thanks for the suggestion. I've built and tested a kernel with > this change made. Result: no change (same performance as with > 8.2-GENERIC). Any thoughts as to where to go next? Hmm. That seemed the most plausible candidate when I looked at this. Do you use quotas (there is one change in UFS related to quotas)? There are 5 changes that involve sys/kern/vfs_bio.c in 8.2: 209459, 212229, 212562, 212583, and 213890. Can you possibly test out kernels from stable/8 at those revisions on an 8.1 world and see if you can narrow it down futher? Barring that, can you do a binary search of kernels from stable/8 between 8.1 and 8.2 on an 8.1 world to see which commit caused the change in write performance? -- John Baldwin