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From: Arjan van de Ven <arjan@linux.intel.com>
To: David Chinner <dgc@sgi.com>
Cc: Nick Piggin <npiggin@suse.de>,
	"Siddha, Suresh B" <suresh.b.siddha@intel.com>,
	linux-kernel@vger.kernel.org, mingo@elte.hu, ak@suse.de,
	jens.axboe@oracle.com, James.Bottomley@SteelEye.com,
	andrea@suse.de, clameter@sgi.com, akpm@linux-foundation.org,
	andrew.vasquez@qlogic.com, willy@linux.intel.com,
	Zach Brown <zach.brown@oracle.com>
Subject: Re: [rfc] direct IO submission and completion scalability issues
Date: Sun, 03 Feb 2008 20:14:45 -0800	[thread overview]
Message-ID: <47A69135.3060306@linux.intel.com> (raw)
In-Reply-To: <20080204021052.GD155407@sgi.com>

David Chinner wrote:
> Hi Nick,
> 
> When Matthew was describing this work at an LCA presentation (not
> sure whether you were at that presentation or not), Zach came up
> with the idea that allowing the submitting application control the
> CPU that the io completion processing was occurring would be a good
> approach to try.  That is, we submit a "completion cookie" with the
> bio that indicates where we want completion to run, rather than
> dictating that completion runs on the submission CPU.
> 
> The reasoning is that only the higher level context really knows
> what is optimal, and that changes from application to application.

well.. kinda. One of the really hard parts of the submit/completion stuff is that
the slab/slob/slub/slib allocator ends up basically "cycling" memory through the system;
there's a sink of free memory on all the submission cpus and a source of free memory
on the completion cpu. I don't think applications are capable of working out what is
best in this scenario..



  reply	other threads:[~2008-02-04  4:17 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-07-28  1:21 Siddha, Suresh B
2007-07-30 18:20 ` Christoph Lameter
2007-07-30 20:35   ` Siddha, Suresh B
2007-07-31  4:19     ` Nick Piggin
2007-07-31 17:14       ` Siddha, Suresh B
2007-08-01  0:41         ` Nick Piggin
2007-08-01  0:55           ` Siddha, Suresh B
2007-08-01  1:24             ` Nick Piggin
2008-02-03  9:52 ` Nick Piggin
2008-02-03 10:53   ` Pekka Enberg
2008-02-03 11:58     ` Nick Piggin
2008-02-04  2:10   ` David Chinner
2008-02-04  4:14     ` Arjan van de Ven [this message]
2008-02-04  4:40       ` David Chinner
2008-02-04 10:09         ` Nick Piggin
2008-02-05  0:14           ` David Chinner
2008-02-08  7:50             ` Nick Piggin
2008-02-04 18:21     ` Zach Brown
2008-02-04 20:10       ` Jens Axboe
2008-02-04 21:45         ` Arjan van de Ven
2008-02-05  8:24           ` Jens Axboe
2008-02-04 10:12   ` Jens Axboe
2008-02-04 10:31     ` Nick Piggin
2008-02-04 10:33       ` Jens Axboe
2008-02-04 22:28         ` James Bottomley
2008-02-04 10:30   ` Andi Kleen
2008-02-04 21:47   ` Siddha, Suresh B

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