Subject: Re: [patch 0/3] [Announcement] Performance Counters for Linux
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       LKML <linux-kernel@vger.kernel.org>, linux-arch@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Stephane Eranian <eranian@googlemail.com>,
       Eric Dumazet <dada1@cosmosbay.com>,
       Robert Richter <robert.richter@amd.com>,
       Arjan van de Veen <arjan@infradead.org>, Peter Anvin <hpa@zytor.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       David Miller <davem@davemloft.net>
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Date: Sat, 06 Dec 2008 13:34:39 +0100
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On Sat, 2008-12-06 at 11:05 +1100, Paul Mackerras wrote:
> Now, the tables in perfmon's user-land libpfm that describe the
> mapping from abstract events to event-selector values and the
> constraints on what events can be counted together come to nearly
> 29,000 lines of code just for the IBM 64-bit powerpc processors.
> 
> Your API condemns us to adding all that bloat to the kernel, plus the
> code to use those tables.

Since you need those tables and that code anyway, and in a solid
reliable way, what is the objection of carrying it in the kernel?

Furthermore, is there a good technical reason these cpus are so
complicated to use?

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