From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Christoph Lameter <cl@linux.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nick Piggin <npiggin@kernel.dk>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH 13/15] x86: add cmpxchg_flag() variant
Date: Wed, 24 Aug 2011 13:15:54 -0700 [thread overview]
Message-ID: <4E555BFA.3010801@goop.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1108241408310.30776@router.home>
On 08/24/2011 12:27 PM, Christoph Lameter wrote:
> On Wed, 24 Aug 2011, Jeremy Fitzhardinge wrote:
>
>> I only looked in arch/x86, but I didn't find any that were
>> straightforward candidates for cmpxchg_flag.
> Look at core code: mm/slub.c
These changes are currently only in arch/x86. I haven't looked at
extending the cmpxchg API kernel-wide.
> But still the solution with the flags would save another instruction and
> the generated code would not be as ugly. For not only do you have an
> additional sete you will then also have to check the result again. This
> means at least two additional instruction.
Sure. And the asm goto() variant avoids the sete and subsequent
gcc-generated test, but at the cost of generating a number of
unnecessary jumps - so it doesn't look like much of a win. Perhaps a
hypothetical gcc extension to add "cc" as an output for asms would help,
but that's conjecture at this point.
J
next prev parent reply other threads:[~2011-08-24 22:43 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-22 23:14 [PATCH 00/12] x86: Ticket lock cleanup Jeremy Fitzhardinge
[not found] ` <cover.1314054734.git.jeremy.fitzhardinge@citrix.com>
2011-08-22 23:14 ` [PATCH 01/15] x86/ticketlock: clean up types and accessors Jeremy Fitzhardinge
2011-08-22 23:14 ` [PATCH 02/15] x86/ticketlock: convert spin loop to C Jeremy Fitzhardinge
2011-08-22 23:14 ` [PATCH 03/15] x86/ticketlock: Use C for __ticket_spin_unlock Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 04/15] x86/ticketlock: make large and small ticket versions of spin_lock the same Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 05/15] x86/ticketlock: make __ticket_spin_lock common Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 06/15] x86/ticketlock: make __ticket_spin_trylock common Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 07/15] x86: add xadd helper macro Jeremy Fitzhardinge
2011-08-22 23:29 ` H. Peter Anvin
2011-08-22 23:43 ` Jeremy Fitzhardinge
2011-08-23 4:41 ` H. Peter Anvin
2011-08-23 10:59 ` Peter Zijlstra
2011-08-23 16:34 ` Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 08/15] x86/ticketlock: use xadd helper Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 09/15] x86/cmpxchg: linux/alternative.h has LOCK_PREFIX Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 10/15] x86/cmpxchg: move 32-bit __cmpxchg_wrong_size to match 64 bit Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 11/15] x86/cmpxchg: move 64-bit set64_bit() to match 32-bit Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 12/15] x86/cmpxchg: unify cmpxchg into cmpxchg.h Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 13/15] x86: add cmpxchg_flag() variant Jeremy Fitzhardinge
2011-08-23 19:01 ` Christoph Lameter
2011-08-23 19:22 ` H. Peter Anvin
2011-08-23 19:52 ` Christoph Lameter
2011-08-23 21:03 ` H. Peter Anvin
2011-08-23 19:53 ` Jeremy Fitzhardinge
2011-08-23 20:45 ` H. Peter Anvin
2011-08-23 22:15 ` Jeremy Fitzhardinge
2011-08-23 22:43 ` H. Peter Anvin
2011-08-24 13:54 ` Christoph Lameter
2011-08-24 13:53 ` Christoph Lameter
2011-08-24 16:33 ` Jeremy Fitzhardinge
2011-08-24 19:27 ` Christoph Lameter
2011-08-24 20:15 ` Jeremy Fitzhardinge [this message]
2011-08-24 20:31 ` H. Peter Anvin
2011-08-24 20:38 ` Jeremy Fitzhardinge
2011-08-24 23:04 ` H. Peter Anvin
2011-08-24 23:11 ` Linus Torvalds
2011-08-24 23:19 ` Jeremy Fitzhardinge
2011-08-25 14:07 ` Christoph Lameter
2011-08-22 23:15 ` [PATCH 14/15] x86/ticketlocks: use cmpxchg_flag for trylock Jeremy Fitzhardinge
2011-08-22 23:15 ` [PATCH 15/15] x86: use cmpxchg_flag() where applicable Jeremy Fitzhardinge
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