Re: [Xen-devel] Linux spin lock enhancement on xen

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

How does this compare with Jeremy's existing paravirtualised spinlocks in
pv_ops? They required no hypervsior changes. Cc'ing Jeremy.

 -- Keir

On 17/08/2010 02:33, "Mukesh Rathor" <mukesh.rathor@xxxxxxxxxx> wrote:

> Hi guys,
> 
> Check out the attached patches. I changed the spin lock semantics so the
> lock contains the vcpu id of the vcpu holding it. This then tells xen
> to make that vcpu runnable if not already running:
> 
> Linux:
>    spin_lock()
>        if (try_lock() == failed)
>            loop X times
>            if (try_lock() == failed)
>                sched_op_yield_to(vcpu_num of holder)
>                start again;
>            endif
>        endif
> 
> Xen:
>      sched_op_yield_to:
>           if (vcpu_running(vcpu_num arg))
>               do nothing
>           else
>               vcpu_kick(vcpu_num arg)
>               do_yield()
>           endif
> 
> 
> In my worst case test scenario, I get about 20-36% improvement when the
> system is two to three times over provisioned.
> 
> Please provide any feedback. I would like to submit official patch for
> SCHEDOP_yield_to in xen.
> 
> thanks,
> Mukesh
> 



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