Re: [PATCH 9/16] 2.6.17-rc6 perfmon2 patch for review: kernel-level API support (kapi)

["Frank Ch. Eigler" <fche@redhat.com>]

Hi -

> > Whether one uses systemtap, raw kprobes, or some specialized
> > tracing/stats-collecting patch surely forthcoming, kernel-level APIs
> > would be needed to perform fine-grained kernel-scope measurements
> > using these counters.
> 
> No, there's not need to add kernel bloat for performance monitoring.
> This kind of stuff shoul dabsolutely be done from userspace.

Userspace measurements provide only large-grained quantities.  Can you
argue convincingly that there is never a need to measure focused
quantities such as cache behaviors of individual subsystems, branch
prediction statistics of a new algorithm?  That running system-level
benchmarks is the most efficient way for developers to assess their
changes?  That the scheduler would not benefit from access to HT
resource utilization statistics?  All these sorts of efforts seem
to require a kernel-side perfmon API.

- FChE