From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
David Vrabel <david.vrabel@citrix.com>,
Waiman Long <Waiman.Long@hp.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Peter Zijlstra <peterz@infradead.org>,
virtualization@lists.linux-foundation.org,
Andi Kleen <andi@firstfloor.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Michel Lespinasse <walken@google.com>,
Alok Kataria <akataria@vmware.com>,
linux-arch@vger.kernel.org, x86@kernel.org,
Ingo Molnar <mingo@redhat.com>,
Scott J Norton <scott.norton@hp.com>,
xen-devel@lists.xenproject.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Alexander Fyodorov <halcy@yandex.ru>,
Rik van Riel <riel@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Daniel J Blueman <daniel@numascale.com>,
Oleg Nesterov <oleg@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Chris Wright <chrisw@sous-sol.org>,
George Spelvin <linux@horizon.com>,
Thomas Gleixner <tglx@linutronix.de>,
Aswin Chandramouleeswaran <aswin@hp.com>,
Chegu
Subject: Re: [PATCH RFC v5 7/8] pvqspinlock, x86: Add qspinlock para-virtualization support
Date: Thu, 27 Feb 2014 20:52:57 +0530 [thread overview]
Message-ID: <530F5851.1090809@linux.vnet.ibm.com> (raw)
In-Reply-To: <530F4F98.2080308@redhat.com>
On 02/27/2014 08:15 PM, Paolo Bonzini wrote:
[...]
>> But neither of the VCPUs being kicked here are halted -- they're either
>> running or runnable (descheduled by the hypervisor).
>
> /me actually looks at Waiman's code...
>
> Right, this is really different from pvticketlocks, where the *unlock*
> primitive wakes up a sleeping VCPU. It is more similar to PLE
> (pause-loop exiting).
Adding to the discussion, I see there are two possibilities here,
considering that in undercommit cases we should not exceed
HEAD_SPIN_THRESHOLD,
1. the looping vcpu in pv_head_spin_check() should do halt()
considering that we have done enough spinning (more than typical
lock-hold time), and hence we are in potential overcommit.
2. multiplex kick_cpu to do directed yield in qspinlock case.
But this may result in some ping ponging?
next prev parent reply other threads:[~2014-02-27 15:22 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-26 15:14 [PATCH v5 0/8] qspinlock: a 4-byte queue spinlock with PV support Waiman Long
2014-02-26 15:14 ` [PATCH v5 1/8] qspinlock: Introducing a 4-byte queue spinlock implementation Waiman Long
2014-02-26 16:22 ` Peter Zijlstra
2014-02-27 20:25 ` Waiman Long
2014-02-26 16:24 ` Peter Zijlstra
2014-02-27 20:25 ` Waiman Long
2014-02-26 15:14 ` [PATCH v5 2/8] qspinlock, x86: Enable x86-64 to use queue spinlock Waiman Long
2014-02-26 15:14 ` [PATCH v5 3/8] qspinlock, x86: Add x86 specific optimization for 2 contending tasks Waiman Long
2014-02-26 16:20 ` Peter Zijlstra
2014-02-27 20:42 ` Waiman Long
2014-02-28 9:29 ` Peter Zijlstra
2014-02-28 16:25 ` Linus Torvalds
2014-02-28 17:37 ` Peter Zijlstra
2014-02-28 16:38 ` Waiman Long
2014-02-28 17:56 ` Peter Zijlstra
2014-03-03 17:43 ` Peter Zijlstra
2014-03-04 15:27 ` Waiman Long
2014-03-04 16:58 ` Peter Zijlstra
2014-03-04 18:09 ` Peter Zijlstra
2014-03-04 17:48 ` Waiman Long
2014-03-04 22:40 ` Peter Zijlstra
2014-03-05 20:59 ` Peter Zijlstra
2014-02-26 15:14 ` [PATCH RFC v5 4/8] pvqspinlock, x86: Allow unfair spinlock in a real PV environment Waiman Long
2014-02-26 17:07 ` Konrad Rzeszutek Wilk
2014-02-28 17:06 ` Waiman Long
2014-03-03 10:55 ` Paolo Bonzini
2014-03-04 15:15 ` Waiman Long
2014-03-04 15:23 ` Paolo Bonzini
2014-03-04 15:39 ` David Vrabel
2014-03-04 17:50 ` Raghavendra K T
2014-02-27 12:28 ` David Vrabel
2014-02-27 19:40 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 5/8] pvqspinlock, x86: Enable unfair queue spinlock in a KVM guest Waiman Long
2014-02-26 17:08 ` Konrad Rzeszutek Wilk
2014-02-28 17:08 ` Waiman Long
2014-02-27 9:41 ` Paolo Bonzini
2014-02-27 19:05 ` Waiman Long
2014-02-27 10:40 ` Raghavendra K T
2014-02-27 19:12 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 6/8] pvqspinlock, x86: Rename paravirt_ticketlocks_enabled Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 7/8] pvqspinlock, x86: Add qspinlock para-virtualization support Waiman Long
2014-02-26 17:54 ` Konrad Rzeszutek Wilk
2014-02-27 12:11 ` David Vrabel
2014-02-27 13:11 ` Paolo Bonzini
2014-02-27 14:18 ` David Vrabel
2014-02-27 14:45 ` Paolo Bonzini
2014-02-27 15:22 ` Raghavendra K T [this message]
2014-02-27 15:50 ` Paolo Bonzini
2014-03-03 11:06 ` [Xen-devel] " David Vrabel
2014-02-27 20:50 ` Waiman Long
2014-02-27 19:42 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 8/8] pvqspinlock, x86: Enable KVM to use qspinlock's PV support Waiman Long
2014-02-27 9:31 ` Paolo Bonzini
2014-02-27 18:36 ` Waiman Long
2014-02-26 17:00 ` [PATCH v5 0/8] qspinlock: a 4-byte queue spinlock with " Konrad Rzeszutek Wilk
2014-02-28 16:56 ` Waiman Long
2014-02-26 22:26 ` Paul E. McKenney
-- strict thread matches above, loose matches on Subject: below --
2014-02-27 4:32 Waiman Long
2014-02-27 4:32 ` [PATCH RFC v5 7/8] pvqspinlock, x86: Add qspinlock para-virtualization support Waiman Long
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