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From: Andi Kleen <andi@firstfloor.org>
To: Nick Piggin <npiggin@suse.de>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
	linux-kernel@vger.kernel.org, arjan@linux.intel.com,
	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: Mon, 4 Feb 2008 11:30:01 +0100	[thread overview]
Message-ID: <20080204103001.GA2674@basil.nowhere.org> (raw)
In-Reply-To: <20080203095252.GA11043@wotan.suse.de>

> +	q = &__get_cpu_var(call_single_queue);
> +	spin_lock_irqsave(&q->lock, flags);
> +	list_replace_init(&q->list, &list);
> +	spin_unlock_irqrestore(&q->lock, flags);

I think you could do that lockless if you use a similar data structure
as netchannels (essentially a fixed size single buffer queue with atomic 
exchange of the first/last pointers) and not using a list. That would avoid 
at least one bounce for the lock and likely another one for the  list
manipulation.

Also the right way would be to not add a second mechanism for this,
but fix the standard smp_call_function_single() to support it.

-Andi

  parent reply	other threads:[~2008-02-04 10:30 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
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 [this message]
2008-02-04 21:47   ` Siddha, Suresh B

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