From: Jens Axboe <jens.axboe@oracle.com>
To: Mark Lord <liml@rtr.ca>
Cc: Mark Lord <lkml@rtr.ca>, Matthew Wilcox <matthew@wil.cx>,
IDE/ATA development list <linux-ide@vger.kernel.org>,
Linux Kernel <linux-kernel@vger.kernel.org>,
linux-scsi <linux-scsi@vger.kernel.org>
Subject: Re: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ?
Date: Thu, 13 Dec 2007 20:53:50 +0100 [thread overview]
Message-ID: <20071213195350.GH10104@kernel.dk> (raw)
In-Reply-To: <47618B0B.8020203@rtr.ca>
On Thu, Dec 13 2007, Mark Lord wrote:
> Jens Axboe wrote:
> >On Thu, Dec 13 2007, Mark Lord wrote:
> >>Mark Lord wrote:
> >>>Jens Axboe wrote:
> >>>>On Thu, Dec 13 2007, Mark Lord wrote:
> >>>>>Matthew Wilcox wrote:
> >>>>>>On Thu, Dec 13, 2007 at 01:48:18PM -0500, Mark Lord wrote:
> >>>>>>>Problem confirmed. 2.6.23.8 regularly generates segments up to
> >>>>>>>64KB for libata,
> >>>>>>>but 2.6.24 uses only 4KB segments and a *few* 8KB segments.
> >>>>>>Just a suspicion ... could this be slab vs slub? ie check your
> >>>>>>configs
> >>>>>>are the same / similar between the two kernels.
> >>>>>..
> >>>>>
> >>>>>Mmmm.. a good thought, that one.
> >>>>>But I just rechecked, and both have CONFIG_SLAB=y
> >>>>>
> >>>>>My guess is that something got changed around when Jens
> >>>>>reworked the block layer for 2.6.24.
> >>>>>I'm going to dig around in there now.
> >>>>I didn't rework the block layer for 2.6.24 :-). The core block layer
> >>>>changes since 2.6.23 are:
> >>>>
> >>>>- Support for empty barriers. Not a likely candidate.
> >>>>- Shared tag queue fixes. Totally unlikely.
> >>>>- sg chaining support. Not likely.
> >>>>- The bio changes from Neil. Of the bunch, the most likely suspects in
> >>>> this area, since it changes some of the code involved with merges and
> >>>> blk_rq_map_sg().
> >>>>- Lots of simple stuff, again very unlikely.
> >>>>
> >>>>Anyway, it sounds odd for this to be a block layer problem if you do see
> >>>>occasional segments being merged. So it sounds more like the input data
> >>>>having changed.
> >>>>
> >>>>Why not just bisect it?
> >>>..
> >>>
> >>>Because the early 2.6.24 series failed to boot on this machine
> >>>due to bugs in the block layer -- so the code that caused this regression
> >>>is probably in the stuff from before the kernels became usable here.
> >>..
> >>
> >>That sounds more harsh than intended --> the earlier 2.6.24 kernels (up to
> >>the first couple of -rc* ones failed here because of incompatibilities
> >>between the block/bio changes and libata.
> >>
> >>That's better, I think!
> >
> >No worries, I didn't pick it up as harsh just as an odd conclusion :-)
> >
> >If I were you, I'd just start from the first -rc that booted for you. If
> >THAT has the bug, then we'll think of something else. If you don't get
> >anywhere, I can run some tests tomorrow and see if I can reproduce it
> >here.
> ..
>
> I believe that *anyone* can reproduce it, since it's broken long before
> the requests ever get to SCSI or libata. Which also means that *anyone*
> who wants to can bisect it, as well.
>
> I don't do "bisects".
It was just a suggestion on how to narrow it down, do as you see fit.
> But I will dig a bit more and see if I can find the culprit.
Sure, I'll dig around as well.
--
Jens Axboe
next prev parent reply other threads:[~2007-12-13 19:54 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-13 18:36 QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Mark Lord
2007-12-13 18:37 ` Mark Lord
2007-12-13 18:42 ` Matthew Wilcox
2007-12-13 18:46 ` James Bottomley
2007-12-13 18:48 ` Mark Lord
2007-12-13 18:53 ` Matthew Wilcox
2007-12-13 19:03 ` Mark Lord
2007-12-13 19:26 ` Jens Axboe
2007-12-13 19:30 ` Mark Lord
2007-12-13 19:32 ` Mark Lord
2007-12-13 19:39 ` Jens Axboe
2007-12-13 19:42 ` Mark Lord
2007-12-13 19:53 ` Jens Axboe [this message]
2007-12-13 19:59 ` Mark Lord
2007-12-13 20:05 ` Jens Axboe
2007-12-13 20:02 ` Jens Axboe
2007-12-13 20:06 ` Mark Lord
2007-12-13 20:09 ` Jens Axboe
2007-12-13 20:14 ` Mark Lord
2007-12-13 20:18 ` Mark Lord
2007-12-13 20:21 ` Jens Axboe
2007-12-13 22:02 ` Andrew Morton
2007-12-13 22:15 ` James Bottomley
2007-12-13 22:29 ` Andrew Morton
2007-12-13 22:33 ` Mark Lord
2007-12-13 23:13 ` Mark Lord
2007-12-14 0:05 ` Mark Lord
2007-12-14 0:30 ` Mark Lord
2007-12-14 0:37 ` Andrew Morton
2007-12-14 0:42 ` Mark Lord
2007-12-14 0:46 ` [PATCH] fix page_alloc for larger I/O segments (improved) Mark Lord
2007-12-14 0:57 ` James Bottomley
2007-12-14 1:11 ` Andrew Morton
2007-12-14 2:23 ` Mark Lord
2007-12-14 17:42 ` Mel Gorman
2007-12-14 18:07 ` Mark Lord
2007-12-16 21:56 ` Mel Gorman
2007-12-14 18:13 ` Matthew Wilcox
2007-12-14 18:30 ` Mark Lord
2007-12-20 22:37 ` Matthew Wilcox
2007-12-14 0:47 ` QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Mark Lord
2007-12-14 11:50 ` Mel Gorman
2007-12-14 13:57 ` Mark Lord
2007-12-14 0:40 ` [PATCH] fix page_alloc for larger I/O segments Mark Lord
2007-12-14 1:03 ` Andrew Morton
2007-12-14 4:00 ` Matthew Wilcox
2007-12-15 1:09 ` QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Mel Gorman
2007-12-15 2:02 ` Andrew Morton
2007-12-15 5:55 ` Matt Mackall
2007-12-16 21:55 ` Mel Gorman
2007-12-17 19:24 ` Randy Dunlap
2007-12-18 2:42 ` Matt Mackall
2007-12-13 22:17 ` Jens Axboe
2007-12-13 22:02 ` VM allocates pages in reverse order again Matthew Wilcox
2007-12-13 19:37 ` QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Jens Axboe
2007-12-13 19:53 ` Mark Lord
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