From: William Lee Irwin III <wli@holomorphy.com>
To: Nikita Danilov <Nikita@Namesys.COM>
Cc: Robert White <rwhite@casabyte.com>,
Nick Piggin <piggin@cyberone.com.au>,
elladan@eskimo.com, Rik van Riel <riel@imladris.surriel.com>,
David Woodhouse <dwmw2@infradead.org>,
ptb@it.uc3m.es, "Martin J. Bligh" <mbligh@aracnet.com>,
linux-kernel@vger.kernel.org, root@chaos.analogic.com
Subject: Re: recursive spinlocks. Shoot.
Date: Fri, 23 May 2003 05:18:38 -0700 [thread overview]
Message-ID: <20030523121838.GY8978@holomorphy.com> (raw)
In-Reply-To: <16077.52259.718519.389903@laputa.namesys.com>
On Fri, May 23, 2003 at 11:22:11AM +0400, Nikita Danilov wrote:
> and suppose they both are equally correct. Now, in (2) total amount of
> time &lock is held is smaller than in (1), but (2) will usually perform
> worse on SMP, because:
> . spin_lock() is an optimization barrier
> . taking even un-contended spin lock is an expensive operation, because
> of the cache coherency issues.
All good. Also, the arrival rate (i.e. frequency of lock acquisition)
is more important to lock contention than hold time, so they're actually
not being as friendly to big SMP as the comment from Robert White would
suggest. The arrival rate tends to be O(cpus) since whatever codepath
pounds on a lock on one cpu can be executed on all simultaneously.
-- wli
next prev parent reply other threads:[~2003-05-23 12:07 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-18 9:21 recursive spinlocks. Shoot Peter T. Breuer
2003-05-18 16:30 ` Martin J. Bligh
2003-05-18 16:35 ` William Lee Irwin III
2003-05-18 16:49 ` Arjan van de Ven
2003-05-18 16:54 ` William Lee Irwin III
2003-05-18 17:14 ` Martin J. Bligh
2003-05-18 17:24 ` Peter T. Breuer
2003-05-18 22:34 ` David Woodhouse
2003-05-19 13:37 ` Peter T. Breuer
2003-05-19 13:45 ` Jens Axboe
2003-05-19 13:47 ` Arjan van de Ven
[not found] ` <mailman.1053352200.24653.linux-kernel2news@redhat.com>
2003-05-19 23:54 ` Pete Zaitcev
2003-05-20 0:03 ` viro
2003-05-20 0:03 ` Johannes Erdfelt
2003-05-20 3:12 ` Robert White
2003-05-20 11:59 ` Helge Hafting
2003-05-20 12:23 ` Richard B. Johnson
2003-05-20 21:05 ` Robert White
2003-05-20 21:42 ` Richard B. Johnson
2003-05-20 23:06 ` Robert White
2003-05-21 14:01 ` Richard B. Johnson
2003-05-21 21:56 ` Robert White
2003-05-22 0:13 ` viro
2003-05-22 0:32 ` Robert White
2003-05-22 0:46 ` Carl-Daniel Hailfinger
2003-05-21 5:48 ` Nikita Danilov
2003-05-22 1:00 ` Rik van Riel
2003-05-22 3:11 ` Robert White
2003-05-22 4:04 ` Nick Piggin
2003-05-22 4:42 ` Peter T. Breuer
2003-05-22 5:09 ` Nick Piggin
2003-05-23 0:19 ` Robert White
2003-05-23 7:22 ` Nikita Danilov
2003-05-23 9:07 ` Helge Hafting
2003-05-23 12:18 ` William Lee Irwin III [this message]
2003-05-24 2:39 ` Robert White
2003-05-28 16:50 ` Timothy Miller
2003-05-19 2:05 ` Kevin O'Connor
2003-05-19 6:19 ` Jan Hudec
2003-05-19 10:29 ` Helge Hafting
2003-05-19 11:37 ` Nikita Danilov
2003-05-22 1:21 ` Daniel Phillips
2003-05-19 14:28 ` Martin J. Bligh
2003-05-18 18:13 ` Davide Libenzi
[not found] <20030518182010$0541@gated-at.bofh.it>
2003-05-18 19:09 ` Peter T. Breuer
2003-05-18 19:31 ` Davide Libenzi
2003-05-18 19:49 ` Peter T. Breuer
2003-05-18 20:13 ` Davide Libenzi
2003-05-19 20:47 ` Jan Hudec
[not found] <20030518202013$5297@gated-at.bofh.it>
2003-05-18 23:15 ` Peter T. Breuer
2003-05-18 23:26 ` Davide Libenzi
2003-05-19 12:48 ` Peter T. Breuer
2003-05-19 17:15 ` Davide Libenzi
2003-05-19 17:27 ` Peter T. Breuer
2003-05-19 17:57 ` Alan Cox
2003-05-19 19:51 ` Peter T. Breuer
2003-05-19 20:22 ` Robert White
[not found] <20030520231013$3d77@gated-at.bofh.it>
2003-05-21 14:16 ` Peter T. Breuer
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