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From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Eric Northup <digitaleric@google.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>, Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>, KVM <kvm@vger.kernel.org>,
	Andi Kleen <andi@firstfloor.org>,
	Xen Devel <xen-devel@lists.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH 06/13] x86/ticketlock: add slowpath logic
Date: Fri, 02 Sep 2011 12:32:25 -0700	[thread overview]
Message-ID: <4E612F49.9080100@goop.org> (raw)
In-Reply-To: <CAG7+5M0s76O_TWBaoY2KU+WeEoJYEhkLLDXfg81WHYNvavH3yw@mail.gmail.com>

On 09/02/2011 11:46 AM, Eric Northup wrote:
> On Thu, Sep 1, 2011 at 5:54 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
>>
>> Maintain a flag in both LSBs of the ticket lock which indicates whether
>> anyone is in the lock slowpath and may need kicking when the current
>> holder unlocks.  The flags are set when the first locker enters
>> the slowpath, and cleared when unlocking to an empty queue.
> Are there actually two flags maintained?  I only see the one in the
> ticket tail getting set/cleared/tested.

Yeah, there's only one flag, so there's a spare bit in the other half.

    j


  reply	other threads:[~2011-09-02 19:32 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-02  0:54 [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 01/13] x86/spinlocks: replace pv spinlocks with pv ticketlocks Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 02/13] x86/ticketlock: collapse a layer of functions Jeremy Fitzhardinge
2011-09-02  0:54   ` Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 03/13] xen/pvticketlock: Xen implementation for PV ticket locks Jeremy Fitzhardinge
2011-09-02  0:54   ` Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 04/13] x86/pvticketlock: use callee-save for lock_spinning Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 05/13] x86/ticketlocks: when paravirtualizing ticket locks, increment by 2 Jeremy Fitzhardinge
2011-09-02  0:54 ` [PATCH 06/13] x86/ticketlock: add slowpath logic Jeremy Fitzhardinge
2011-09-02 18:46   ` Eric Northup
2011-09-02 19:32     ` Jeremy Fitzhardinge [this message]
2011-09-02  0:55 ` [PATCH 07/13] x86/ticketlocks: tidy up __ticket_unlock_kick() Jeremy Fitzhardinge
2011-09-02  0:55 ` [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking Jeremy Fitzhardinge
2011-09-02 14:47   ` Peter Zijlstra
2011-09-02 19:29     ` Jeremy Fitzhardinge
2011-09-02 19:29       ` Jeremy Fitzhardinge
2011-09-02 20:47       ` Peter Zijlstra
2011-09-02 20:47         ` Peter Zijlstra
2011-09-02 21:50         ` Jeremy Fitzhardinge
2011-09-02 22:37           ` Peter Zijlstra
2011-09-02 22:37             ` Peter Zijlstra
2011-09-02 23:14           ` Andi Kleen
2011-09-05 11:52           ` Stefano Stabellini
2011-09-05 12:05           ` Avi Kivity
2011-09-06 15:14           ` Don Zickus
2011-09-06 18:07             ` Jeremy Fitzhardinge
2011-09-06 18:27               ` Don Zickus
2011-09-06 18:50                 ` Jeremy Fitzhardinge
2011-09-06 18:50                   ` Jeremy Fitzhardinge
2011-09-07  4:13                 ` Avi Kivity
2011-09-07 13:44                   ` Don Zickus
2011-09-07 13:44                     ` Don Zickus
2011-09-07 15:11                     ` Avi Kivity
2011-09-07 15:11                       ` Avi Kivity
2011-09-07 15:56                       ` Don Zickus
2011-09-07 15:56                         ` Don Zickus
2011-09-07 16:25                         ` Avi Kivity
2011-09-07 16:52                           ` Don Zickus
2011-09-07 17:09                             ` Avi Kivity
2011-09-07 17:17                               ` Jeremy Fitzhardinge
2011-09-07 17:41                                 ` Avi Kivity
2011-09-07 19:09                                   ` Jeremy Fitzhardinge
2011-09-08  7:51                                     ` Avi Kivity
2011-09-08 17:29                                       ` Jeremy Fitzhardinge
2011-09-08 17:29                                         ` Jeremy Fitzhardinge
2011-09-11  9:59                                         ` Avi Kivity
2011-09-11  9:59                                           ` Avi Kivity
2011-09-07 17:21                               ` Don Zickus
2011-09-07 17:21                                 ` Don Zickus
2011-09-07 17:41                                 ` Avi Kivity
2011-09-13 18:40                               ` Don Zickus
2011-09-13 19:03                                 ` Andi Kleen
2011-09-13 19:21                                   ` Don Zickus
2011-09-13 19:21                                     ` Don Zickus
2011-09-13 19:58                                     ` Andi Kleen
2011-09-13 20:53                                       ` Don Zickus
2011-09-13 21:04                                         ` Andi Kleen
2011-09-14  7:00                                     ` Avi Kivity
2011-09-14 12:49                                       ` Don Zickus
2011-09-14 12:49                                         ` Don Zickus
2011-09-14 14:49                                       ` Andi Kleen
2011-09-14 15:01                                         ` Avi Kivity
2011-09-14 17:28                                           ` Andi Kleen
2011-09-14 17:28                                             ` Andi Kleen
2011-09-14 19:26                                             ` Avi Kivity
2011-09-14 19:34                                               ` Andi Kleen
2011-09-14 19:34                                                 ` Andi Kleen
2011-09-14 19:56                                                 ` Avi Kivity
2011-09-13 19:27                                   ` Don Zickus
2011-09-02  0:55 ` [PATCH 09/13] x86/pvticketlocks: we only need to kick if there's waiters Jeremy Fitzhardinge
2011-09-02  0:55 ` [PATCH 10/13] xen/pvticket: allow interrupts to be enabled while blocking Jeremy Fitzhardinge
2011-09-02 14:48   ` Peter Zijlstra
2011-09-02 19:30     ` Jeremy Fitzhardinge
2011-09-02  0:55 ` [PATCH 11/13] x86/ticketlock: only do kick after doing unlock Jeremy Fitzhardinge
2011-09-02 14:49   ` Peter Zijlstra
2011-09-02 19:34     ` Jeremy Fitzhardinge
2011-09-02 19:34       ` Jeremy Fitzhardinge
2011-09-02  0:55 ` [PATCH 12/13] x86/pvticketlock: make sure unlock_kick pvop call is inlined Jeremy Fitzhardinge
2011-09-02  0:55 ` [PATCH 13/13] x86/pvticketlock: use __ticket_t for pvop args Jeremy Fitzhardinge
2011-09-02 11:22 ` [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks Stefano Stabellini
2011-09-02 11:22   ` Stefano Stabellini
2011-09-06 19:33   ` Jeremy Fitzhardinge
2011-09-02 15:38 ` Linus Torvalds
2011-09-02 20:07   ` Jeremy Fitzhardinge
2011-09-02 20:27     ` Linus Torvalds
2011-09-02 21:42       ` Jeremy Fitzhardinge

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