perf_counter: Start documenting HAVE_PERF_COUNTERS requirements

Help out arch porters who want to support perf counters by listing some
basic requirements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1244827063-24046-1-git-send-email-vapier@gentoo.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Frysinger 2009-06-12 13:17:43 -04:00 committed by Ingo Molnar
parent 974802eaa1
commit 018df72dd0
2 changed files with 17 additions and 0 deletions

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@ -936,6 +936,8 @@ config AIO
config HAVE_PERF_COUNTERS
bool
help
See tools/perf/design.txt for details.
menu "Performance Counters"

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@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
this process has created on other processes. It only enables or
disables the group leaders, not any other members in the groups.
Arch requirements
-----------------
If your architecture does not have hardware performance metrics, you can
still use the generic software counters based on hrtimers for sampling.
So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
will need at least this:
- asm/perf_counter.h - a basic stub will suffice at first
- support for atomic64 types (and associated helper functions)
- set_perf_counter_pending() implemented
If your architecture does have hardware capabilities, you can override the
weak stub hw_perf_counter_init() to register hardware counters.