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Re: [Xen-devel] [RFC] Implement Batched (group) ticket lock

On 05/29/2014 12:16 PM, Peter Zijlstra wrote:
On Wed, May 28, 2014 at 05:46:39PM +0530, Raghavendra K T wrote:
In virtualized environment there are mainly three problems
related to spinlocks that affect performance.
1. LHP (lock holder preemption)
2. Lock Waiter Preemption (LWP)
3. Starvation/fairness

  Though ticketlocks solve the fairness problem, it worsens LWP, LHP problems.
pv-ticketlocks tried to address this. But we can further improve at the
cost of relaxed fairness.

So I really hate the idea of having different locks for paravirt and
normal kernels.

Yes. I understand that queued lock for normal kernel and unfair version of queued spinlock for virtual guest would do better.

Since strict serialization of lockwaiters (in both ticketlock/queued spinlock) does not work well for virtualized guest, my idea was to give an alternate idea which has bounded starvation and performs as good as unfair version to virtualized guest.

And we're looking to move to that queued lock for normal kernels.

Agree. and I have tested that too.

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