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

[Andi Kleen]

> 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.

And using virtual performance counters adds a large cost the 
context switch for changing the MSRs around. An always running counter
avoids this problem.

-Andi
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