Re: [PATCH 02/18] perf: Add persistent event facilities

[Peter Zijlstra <peterz@infradead.org>]

On Sat, 2011-04-23 at 18:28 +0200, Borislav Petkov wrote:
> From: Borislav Petkov <borislav.petkov@amd.com>
> 
> Add a barebones implementation for registering persistent events with
> perf. For that, we don't destroy the buffers when they're unmapped and
> we map them read-only so that multiple agents can access them.
> 
> Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
> ---
>  include/linux/perf_event.h |   22 ++++++++++++++++-
>  kernel/events/Makefile     |    2 +-
>  kernel/events/core.c       |   30 ++++++++++++++++++----
>  kernel/events/persistent.c |   56 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 102 insertions(+), 8 deletions(-)
>  create mode 100644 kernel/events/persistent.c
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index ee9f1e7..37bfae1 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -216,8 +216,9 @@ struct perf_event_attr {
>                                 precise_ip     :  2, /* skid constraint       */
>                                 mmap_data      :  1, /* non-exec mmap data    */
>                                 sample_id_all  :  1, /* sample_type all events */
> +                               persistent     :  1, /* event always on */

But how will you find it again?

Persistent yells filesystem to me, and while we didn't use relayfs for
various reasons, I think we do need something like it at the current
stage.