To: perfctr-devel@lists.sourceforge.net
Subject: perfctr-2.0-pre4 released

perfctr-2.0-pre4 is now available at the usual place:
http://www.csd.uu.se/~mikpe/linux/perfctr/.

The new API is in place and seems to work fine.
The split of the old "status" field in three (tsc_on,
nrctrs, and nrictrs) annoys me and I may change this
particular detail slightly. Apart from this and the
non-functioning signal-on-overflow facility, I consider
this to be fairly close to perfctr-2.0 final.

A question: should TSC sampling be mandatory? How often do
people monitor the performance counters while ignoring the TSC?
Sampling the TSC costs cycles, but not sampling it also has
costs (it forces my library to fall back to the system call
when sampling).

Version 2.0-pre4, 2001-04-30
- Some module usage accounting changes which should make automatic
  module loading and unloading more robust in 2.2 kernels.
- Internal cleanups and a few minor bug fixes.
- Some API naming changes, and O_CREAT can now be used to control
  whether opening /proc/self/perfctr should create and attach
  a vperfctr or not.
- The user-space library has been updated for the new API.
  pmc_map[] is used to map from "virtual counter i" to an actual
  PMC index to be used by RDPMC -- the VIA Cyrix III / C3 is now
  able to sample in user-space even though it has no PMC(0).
  The layout of pmc_map[] is CPU-specific; see x86.c for details.
  Since TSC sampling is specified explicitly now, perfctr_cpu_nrctrs()
  has been changed to return the number of performance counters
  _excluding_ the TSC.
- The example programs have been updated for the new API, with the
  exception of signal.c which is still non-functional.
- The perfex.c example works better now that the API has a consistent
  one-evntsel-per-counter model even for Intel P5-like CPUs.
- The global.c example has been fixed to not cause a division by zero
  on WinChip CPUs lacking a working TSC.


/ Mikael Pettersson