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    SubjectRe: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements
    Mike Frysinger wrote:
    > Help out arch porters who want to support perf counters by listing some
    > basic requirements.
    >
    > Signed-off-by: Mike Frysinger <vapier@gentoo.org>
    > ---
    > i imagine more details would be good, but this is a starting point and
    > better than nothing
    >
    > init/Kconfig | 2 ++
    > tools/perf/design.txt | 15 +++++++++++++++
    > 2 files changed, 17 insertions(+), 0 deletions(-)
    >
    > diff --git a/init/Kconfig b/init/Kconfig
    > index c649657..20f85b1 100644
    > --- a/init/Kconfig
    > +++ b/init/Kconfig
    > @@ -936,6 +936,8 @@ config AIO
    >
    > config HAVE_PERF_COUNTERS
    > bool
    > + help
    > + See end of tools/perf/design.txt

    How about
    See "Arch requirements" in tools/perf/design.txt
    since it doesn't need to be at the end of the file forever.

    >
    > menu "Performance Counters"
    >
    > diff --git a/tools/perf/design.txt b/tools/perf/design.txt
    > index 860e116..f71e0d2 100644
    > --- a/tools/perf/design.txt
    > +++ b/tools/perf/design.txt
    > @@ -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.


    --
    ~Randy
    LPC 2009, Sept. 23-25, Portland, Oregon
    http://linuxplumbersconf.org/2009/


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