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Date: Fri, 29 May 2009 08:51:04 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: eranian@gmail.com, LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
       Robert Richter <robert.richter@amd.com>,
       Paul Mackerras <paulus@samba.org>, Andi Kleen <andi@firstfloor.org>,
       Maynard Johnson <mpjohn@us.ibm.com>, Carl Love <cel@us.ibm.com>,
       Corey J Ashford <cjashfor@us.ibm.com>,
       Philip Mucci <mucci@eecs.utk.edu>, Dan Terpstra <terpstra@eecs.utk.edu>,
       perfmon2-devel <perfmon2-devel@lists.sourceforge.net>
Subject: Re: comments on Performance Counters for Linux (PCL)
Message-ID: <20090529065104.GO1065@one.firstfloor.org>
References: <7c86c4470905280758y6d359823h2a7517dfecb115e6@mail.gmail.com> <1243527919.6645.75.camel@laptop>
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> >        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"

-Andi