From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Stephan Diestelhorst <stephan.diestelhorst@amd.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>, Jan Beulich <JBeulich@suse.com>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
Andi Kleen <andi@firstfloor.org>,
Peter Zijlstra <peterz@infradead.org>,
Nick Piggin <npiggin@kernel.dk>,
the arch/x86 maintainers <x86@kernel.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>, KVM <kvm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks
Date: Mon, 10 Oct 2011 12:51:29 -0700 [thread overview]
Message-ID: <4E934CC1.9040804@goop.org> (raw)
In-Reply-To: <20111010073214.GB29035@elte.hu>
On 10/10/2011 12:32 AM, Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>
>> On 10/06/2011 10:40 AM, Jeremy Fitzhardinge wrote:
>>> However, it looks like locked xadd is also has better performance: on
>>> my Sandybridge laptop (2 cores, 4 threads), the add+mfence is 20% slower
>>> than locked xadd, so that pretty much settles it unless you think
>>> there'd be a dramatic difference on an AMD system.
>> Konrad measures add+mfence is about 65% slower on AMD Phenom as well.
> xadd also results in smaller/tighter code, right?
Not particularly, mostly because of the overflow-into-the-high-part
compensation. But its only a couple of extra instructions, and no
conditionals, so I don't think it would have any concrete effect.
But, as Stephen points out, perhaps locked add is preferable to locked
xadd, since it also has the same barrier as mfence but has
(significantly!) better performance than either mfence or locked xadd...
J
next prev parent reply other threads:[~2011-10-10 19:51 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-15 0:31 [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 01/10] x86/ticketlocks: remove obsolete comment Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 02/10] x86/spinlocks: replace pv spinlocks with pv ticketlocks Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 03/10] x86/ticketlock: don't inline _spin_unlock when using paravirt spinlocks Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 04/10] x86/ticketlock: collapse a layer of functions Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 05/10] xen/pvticketlock: Xen implementation for PV ticket locks Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 06/10] x86/pvticketlock: use callee-save for lock_spinning Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 07/10] x86/ticketlocks: when paravirtualizing ticket locks, increment by 2 Jeremy Fitzhardinge
2011-09-15 0:31 ` Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 08/10] x86/ticketlock: add slowpath logic Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 09/10] xen/pvticketlock: allow interrupts to be enabled while blocking Jeremy Fitzhardinge
2011-09-15 0:31 ` [PATCH 10/10] xen: enable PV ticketlocks on HVM Xen Jeremy Fitzhardinge
2011-09-27 9:34 ` [Xen-devel] [PATCH 00/10] [PATCH RFC V2] Paravirtualized ticketlocks Stephan Diestelhorst
2011-09-27 9:34 ` Stephan Diestelhorst
2011-09-27 9:34 ` Stephan Diestelhorst
2011-09-27 16:44 ` [Xen-devel] " Jeremy Fitzhardinge
2011-09-27 16:44 ` Jeremy Fitzhardinge
2011-09-28 13:58 ` [Xen-devel] " Stephan Diestelhorst
2011-09-28 16:44 ` Jeremy Fitzhardinge
2011-09-28 18:13 ` Stephan Diestelhorst
2011-09-28 15:38 ` Linus Torvalds
2011-09-28 15:55 ` Jan Beulich
2011-09-28 15:55 ` Jan Beulich
2011-09-28 16:10 ` Linus Torvalds
2011-09-28 16:47 ` Jeremy Fitzhardinge
2011-09-28 17:22 ` Linus Torvalds
2011-09-28 17:24 ` H. Peter Anvin
2011-09-28 17:50 ` Jeremy Fitzhardinge
2011-09-28 18:08 ` Stephan Diestelhorst
2011-09-28 18:27 ` Jeremy Fitzhardinge
2011-09-28 18:49 ` Linus Torvalds
2011-09-28 19:06 ` Jeremy Fitzhardinge
2011-10-06 14:04 ` Stephan Diestelhorst
2011-10-06 17:40 ` Jeremy Fitzhardinge
2011-10-06 18:09 ` Jeremy Fitzhardinge
2011-10-10 7:32 ` Ingo Molnar
2011-10-10 19:51 ` Jeremy Fitzhardinge [this message]
2011-10-10 11:00 ` Stephan Diestelhorst
2011-10-10 11:00 ` Stephan Diestelhorst
2011-10-10 14:01 ` Stephan Diestelhorst
2011-10-10 14:01 ` Stephan Diestelhorst
2011-10-10 19:44 ` Jeremy Fitzhardinge
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