From: Alasdair G Kergon <agk@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: axboe@kernel.dk, dm-devel <dm-devel@redhat.com>,
Mikulas Patocka <mpatocka@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: Queue upcall locking (was: [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path)
Date: Mon, 10 Nov 2008 14:27:15 +0000 [thread overview]
Message-ID: <20081110142715.GD16649@agk.fab.redhat.com> (raw)
In-Reply-To: <20081110135401.GA11606@infradead.org>
On Mon, Nov 10, 2008 at 08:54:01AM -0500, Christoph Hellwig wrote:
> On Mon, Nov 10, 2008 at 08:11:51AM -0500, Mikulas Patocka wrote:
> > For upstream Linux developers: you are holding a spinlock and calling
> > bdi*_congested functions that can take indefinite amount of time (there
> > are even users reporting having 50 disks in one logical volume or so). I
> > think it would be good to move these calls out of spinlocks.
> Umm, they shouldn't block that long, as that completely defeats their
> purpose.
Indeed - the blocking was a bug for which there's a patch, but that doesn't
deal with how the function should be operating in the first place.
- If one device is found to be congested, why bother checking the remaining
devices?
- If the device is suspended, the response should be that it is congested, I'd
have thought.
Alasdair
--
agk@redhat.com
WARNING: multiple messages have this Message-ID (diff)
From: Alasdair G Kergon <agk@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
axboe@kernel.dk, dm-devel <dm-devel@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: Queue upcall locking (was: [dm-devel] [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path)
Date: Mon, 10 Nov 2008 14:27:15 +0000 [thread overview]
Message-ID: <20081110142715.GD16649@agk.fab.redhat.com> (raw)
In-Reply-To: <20081110135401.GA11606@infradead.org>
On Mon, Nov 10, 2008 at 08:54:01AM -0500, Christoph Hellwig wrote:
> On Mon, Nov 10, 2008 at 08:11:51AM -0500, Mikulas Patocka wrote:
> > For upstream Linux developers: you are holding a spinlock and calling
> > bdi*_congested functions that can take indefinite amount of time (there
> > are even users reporting having 50 disks in one logical volume or so). I
> > think it would be good to move these calls out of spinlocks.
> Umm, they shouldn't block that long, as that completely defeats their
> purpose.
Indeed - the blocking was a bug for which there's a patch, but that doesn't
deal with how the function should be operating in the first place.
- If one device is found to be congested, why bother checking the remaining
devices?
- If the device is suspended, the response should be that it is congested, I'd
have thought.
Alasdair
--
agk@redhat.com
next prev parent reply other threads:[~2008-11-10 14:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-06 4:00 [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path Chandra Seetharaman
2008-11-10 13:11 ` Queue upcall locking (was: [RFC][PATCH] fix dm_any_congested() to properly sync up with suspend code path) Mikulas Patocka
2008-11-10 13:11 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-10 13:54 ` Queue upcall locking (was: " Christoph Hellwig
2008-11-10 13:54 ` Queue upcall locking (was: [dm-devel] " Christoph Hellwig
2008-11-10 14:19 ` Queue upcall locking (was: " Mikulas Patocka
2008-11-10 14:19 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-10 14:26 ` Peter Zijlstra
2008-11-10 14:32 ` Queue upcall locking (was: " Mikulas Patocka
2008-11-10 14:32 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-10 14:46 ` Peter Zijlstra
2008-11-10 14:55 ` Queue upcall locking (was: " Mikulas Patocka
2008-11-10 14:55 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-10 14:35 ` Queue upcall locking (was: " Alasdair G Kergon
2008-11-10 14:35 ` Queue upcall locking (was: [dm-devel] " Alasdair G Kergon
2008-11-11 18:18 ` Queue upcall locking (was: " Christoph Hellwig
2008-11-11 18:18 ` Queue upcall locking (was: [dm-devel] " Christoph Hellwig
2008-11-11 22:08 ` Queue upcall locking (was: " Mikulas Patocka
2008-11-11 22:08 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-10 14:27 ` Alasdair G Kergon [this message]
2008-11-10 14:27 ` Alasdair G Kergon
2008-11-10 14:40 ` Queue upcall locking (was: " Mikulas Patocka
2008-11-10 14:40 ` Queue upcall locking (was: [dm-devel] " Mikulas Patocka
2008-11-11 18:22 ` Christoph Hellwig
2008-11-11 18:21 ` Christoph Hellwig
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