From: Alasdair G Kergon <agk@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Brian Wood <brian.j.wood@intel.com>,
Daniel Walker <dwalker@mvista.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Jonathan Brassow <jbrassow@redhat.com>,
"Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>,
Milan Broz <mbroz@redhat.com>, Paul Jimenez <pj@place.org>,
"Robert P. J. Day" <rpjday@crashcourse.ca>,
Vasily Averin <vvs@sw.ru>,
dm-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [git pull] device-mapper update for 2.6.25
Date: Fri, 8 Feb 2008 03:24:23 +0000 [thread overview]
Message-ID: <20080208032423.GX8075@agk.fab.redhat.com> (raw)
In-Reply-To: <20080207190447.b4dcfe0c.akpm@linux-foundation.org>
On Thu, Feb 07, 2008 at 07:04:47PM -0800, Andrew Morton wrote:
> On Fri, 8 Feb 2008 02:45:32 +0000 Alasdair G Kergon <agk@redhat.com> wrote:
>
> > dm: move deferred bio flushing to workqueue
>
> To my unpracticed eye this one looks fairly fundamental. Unfortunately the
> changelog:
>
> Add a single-thread workqueue for each mapped device and move flushing
> of the lists of pushback and deferred bios to this new workqueue.
>
> tells us nothing of the reasons for this change. (It should have done so!)
>
> It _looks_ pretty unscalable. Perhaps these deferred BIOs don't happen
> very often?
Indeed - it's a rare occurrence - happens when the dm device is
suspended/resumed which usually means it was being reconfigured by something in
userspace.
It's the first patch of a series that will provide barrier support (slated for
2.6.26).
The appearance of all these workqueues in dm goes back to this old change:
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
Alasdair
--
agk@redhat.com
prev parent reply other threads:[~2008-02-08 3:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-08 2:45 Alasdair G Kergon
2008-02-08 3:04 ` Andrew Morton
2008-02-08 3:24 ` Alasdair G Kergon [this message]
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