Re: [Xen-devel] [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Wed, Jul 10, 2013 at 01:33:25PM +0300, Gleb Natapov wrote:

Here's an idea, trim the damn email ;-) -- not only directed at gleb.

> > Ingo, Gleb,
> > 
> > From the results perspective, Andrew Theurer, Vinod's test results are
> > pro-pvspinlock.
> > Could you please help me to know what will make it a mergeable
> > candidate?.
> > 
> I need to spend more time reviewing it :) The problem with PV interfaces
> is that they are easy to add but hard to get rid of if better solution
> (HW or otherwise) appears.

How so? Just make sure the registration for the PV interface is optional; that
is, allow it to fail. A guest that fails the PV setup will either have to try
another PV interface or fall back to 'native'.

> > I agree that Jiannan's Preemptable Lock idea is promising and we could
> > evaluate that  approach, and make the best one get into kernel and also
> > will carry on discussion with Jiannan to improve that patch.
> That would be great. The work is stalled from what I can tell.

I absolutely hated that stuff because it wrecked the native code.

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