Re: [patch 0/3] [Announcement] Performance Counters for Linux

Peter Zijlstra
2008-12-06T12:35:02Z

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?