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Re: [Xen-devel] [PATCH v6 05/11] pvqspinlock, x86: Allow unfair spinlock in a PV guest
- To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- From: Waiman Long <waiman.long@xxxxxx>
- Date: Tue, 18 Mar 2014 23:08:26 -0400
- Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Andi Kleen <andi@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Michel Lespinasse <walken@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, Gleb Natapov <gleb@xxxxxxxxxx>, x86@xxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Scott J Norton <scott.norton@xxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, Oleg Nesterov <oleg@xxxxxxxxxx>, Alok Kataria <akataria@xxxxxxxxxx>, Aswin Chandramouleeswaran <aswin@xxxxxx>, Chegu Vinod <chegu_vinod@xxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 19 Mar 2014 03:09:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On 03/17/2014 02:54 PM, Peter Zijlstra wrote:
On Mon, Mar 17, 2014 at 01:44:34PM -0400, Waiman Long wrote:
The PV ticketlock code was designed to handle lock holder preemption by
redirecting CPU resources in a preempted guest to another guest that can
better use it and then return the preempted CPU back sooner.
But that's the PV code, not the unfair bit. And your fuller PV thing
doesn't need the unfair option.
What I am want to try out is to combine the PV thing with the unfair
lock and see how it performs together. I had set up 2 virtual guests
sharing 20 vCPUs (200% overcommit). Preliminary testing showed that
unfair lock was a bit faster than PV, but PV seems to be a bit more
energy efficient (less total sys+user time). I will have more data to
share tomorrow.
-Longman
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