From: Andi Kleen <ak@suse.de>
To: David Howells <dhowells@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
Arjan van de Ven <arjan@infradead.org>,
Dong Feng <middle.fengdong@gmail.com>,
Paul Mackerras <paulus@samba.org>,
Christoph Lameter <clameter@sgi.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: Why Semaphore Hardware-Dependent?
Date: Tue, 29 Aug 2006 12:56:54 +0200 [thread overview]
Message-ID: <200608291256.54665.ak@suse.de> (raw)
In-Reply-To: <11861.1156845927@warthog.cambridge.redhat.com>
On Tuesday 29 August 2006 12:05, David Howells wrote:
>Because i386 (and x86_64) can do better by using XADDL/XADDQ.
x86-64 has always used the spinlock based version.
> On i386, CMPXCHG also ties you to what registers you may use for what to some
> extent.
We've completely given up these kinds of micro optimization for spinlocks,
which are 1000x as critical as rwsems. And nobody was able to benchmark
a difference.
It is very very likely nobody could benchmark a difference on rwsems either.
While I'm sure it's an interesting intellectual exercise to do these
advanced rwsems it would be better for everybody else to go for a single
maintainable C implementation.
-Andi
next prev parent reply other threads:[~2006-08-29 10:57 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <a2ebde260608271222x2b51693fnaa600965fcfaa6d2@mail.gmail.com>
[not found] ` <1156750249.3034.155.camel@laptopd505.fenrus.org>
2006-08-29 1:18 ` Why Semaphore Hardware-Dependent? Nick Piggin
2006-08-29 6:07 ` Andi Kleen
2006-09-13 17:54 ` Nick Piggin
2006-08-29 10:05 ` David Howells
2006-08-29 10:56 ` Andi Kleen [this message]
2006-08-29 17:40 ` Andrew Morton
2006-08-29 19:10 ` Benjamin LaHaise
2006-08-29 15:56 ` Christoph Lameter
2006-08-29 16:20 ` Ralf Baechle
2006-08-29 16:25 ` David Howells
2006-08-29 16:28 ` Christoph Lameter
2006-08-29 16:57 ` David Howells
2006-08-29 16:53 ` Ralf Baechle
2006-08-29 16:58 ` Geert Uytterhoeven
2006-08-29 17:22 ` Andi Kleen
2006-08-29 17:36 ` Christoph Lameter
2006-08-29 18:18 ` Andi Kleen
2006-08-29 18:30 ` David Howells
2006-08-29 18:33 ` Andi Kleen
2006-08-29 18:56 ` David Howells
2006-08-29 18:41 ` Christoph Lameter
2006-09-13 18:04 ` Nick Piggin
2006-09-13 18:07 ` Christoph Lameter
2006-09-13 18:13 ` Nick Piggin
2006-09-13 18:16 ` Christoph Lameter
2006-09-13 18:50 ` David Howells
2006-09-13 19:25 ` Nick Piggin
2006-09-14 11:41 ` David Howells
2006-09-14 15:27 ` Nick Piggin
2006-09-14 15:38 ` Nick Piggin
2006-09-15 8:59 ` David Howells
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