Re: comments on Performance Counters for Linux (PCL)

From: Andi Kleen
Date: Fri May 29 2009 - 02:44:31 EST

> > Take Itanium, it has 4 priv levels and the PMU counters can monitor at
> > any priv levels or combination thereof?
> x86 has more priv rings too, but linux only uses 2, kernel (ring 0) and
> user (ring 2 iirc). Does ia64 expose more than 2 priv levels in linux?

In a hardware virtualized environment x86 Linux uses at least four.

And yes ia64 also exposes more I believe, e.g. it has the fancy
"system calls that run in user context"


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