Re: [Xen-devel] [PATCH v2] arm: reduce power use by contented spin locks with WFE/SEV

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.08.15 at 13:29, <ian.campbell@xxxxxxxxxx> wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
> 
> Instead of cpu_relax() while spinning and observing the ticket head,
> introduce arch_lock_relax() which executes a WFE instruction.  After
> the ticket head is changed call arch_lock_signal() to execute an SEV
> instruction (with the required DSB first) to wake any spinners.
> 
> This should improve power consumption when locks are contented and
> spinning.

So why not use MONITOR/MWAIT on x86 for the same purpose?

Jan


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