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From: Andi Kleen <andi@firstfloor.org>
To: David Chinner <dgc@sgi.com>, Michael Tokarev <mjt@tls.msk.ru>,
	Ric Wheeler <ric@emc.com>,
	device-mapper development <dm-devel@redhat.com>,
	Andi Kleen <andi@firstfloor.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [dm-devel] Re: [PATCH] Implement barrier support for single device DM devices
Date: Tue, 19 Feb 2008 10:43:48 +0100	[thread overview]
Message-ID: <20080219094348.GE6485@one.firstfloor.org> (raw)
In-Reply-To: <20080219025643.GD4066@agk.fab.redhat.com>

> My complaint about having to support them within dm when more than one
> device is involved is because any efficiencies disappear: you can't send
> further I/O to any one device until all the other devices have completed
> their barrier (or else later I/O to that device could overtake the
> barrier on another device).  And then I argue that it would be better

I was wondering: would it help DM to have the concept of a "barrier window"
As in "this barrier is only affective for this group of requests"
With such a concept DM would need to stall only inside the groups
and possible even issue such barrier groups in parallel, couldn't it?

I'm sure you guys all have thought far more about barriers than
I ever did; if that idea came up before why was it dismissed?

-Andi


  parent reply	other threads:[~2008-02-19  9:43 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-15 12:08 [PATCH] Implement barrier support for single device DM devices Andi Kleen
2008-02-15 12:20 ` Alasdair G Kergon
2008-02-15 13:07   ` Michael Tokarev
2008-02-15 14:20     ` Andi Kleen
2008-02-15 14:12       ` [dm-devel] " Alasdair G Kergon
2008-02-15 15:34         ` Andi Kleen
2008-02-15 15:31           ` Alan Cox
2008-02-18 12:48         ` Ric Wheeler
2008-02-18 13:24           ` Michael Tokarev
2008-02-18 13:52             ` Ric Wheeler
2008-02-19  2:45               ` Alasdair G Kergon
2008-05-16 19:55                 ` Mike Snitzer
2008-05-16 21:48                   ` Andi Kleen
2008-02-18 22:16             ` David Chinner
2008-02-19  2:56               ` Alasdair G Kergon
2008-02-19  5:36                 ` David Chinner
2008-02-19  9:43                 ` Andi Kleen [this message]
2008-02-19  7:19               ` Jeremy Higdon
2008-02-19  7:58                 ` Michael Tokarev
2008-02-20 13:38                 ` Ric Wheeler
2008-02-21  3:29                 ` Neil Brown
2008-02-21  3:39               ` Neil Brown
2008-02-17 23:31     ` David Chinner
2008-02-19  2:39     ` Alasdair G Kergon
2008-02-19 11:12       ` David Chinner

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