Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default

[Andi Kleen <ak@suse.de>]

On Wed, Nov 30, 2005 at 10:56:26AM +1100, David Gibson wrote:
> On Wed, Nov 30, 2005 at 12:39:20AM +0100, Andi Kleen wrote:
> > > Well, if that's all you want them to use RDPMC 0 for, why not just make
> > > PMCs programmable from userspace?
> > 
> > First we need to have a cycle counter PMC anyways for the NMI watchdog.
> > So it can as well be used for other purposes.
> 
> But the watchdog doesn't require it to be in the same place on all
> machines.  Exporting it turns an internal requirement into an ABI
> point.

Yes, but the only alternative I know of would be to let user space
continue getting broken all the time with RDTSC.  RDPMC is a nice
alternative. 

-Andi
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