perf events: Make sample_type identity fields available in all PERF_RECORD_ events

If perf_event_attr.sample_id_all is set it will add the PERF_SAMPLE_ identity
info:

TID, TIME, ID, CPU, STREAM_ID

As a trailer, so that older perf tools can process new files, just ignoring the
extra payload.

With this its possible to do further analysis on problems in the event stream,
like detecting reordering of MMAP and FORK events, etc.

V2: Fixup header size in comm, mmap and task processing, as we have to take into
account different sample_types for each matching event, noticed by Thomas Gleixner.

Thomas also noticed a problem in v2 where if we didn't had space in the buffer we
wouldn't restore the header size.

Tested-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b9950b1620d8..2814ead4adb8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -215,8 +215,9 @@ struct perf_event_attr {
                                  */
                                 precise_ip     :  2, /* skid constraint       */
                                 mmap_data      :  1, /* non-exec mmap data    */
+                                sample_id_all  :  1, /* sample_type all events */
 
-                                __reserved_1   : 46;
+                                __reserved_1   : 45;
 
         union {
                 __u32           wakeup_events;    /* wakeup every n events */
@@ -327,6 +328,15 @@ struct perf_event_header {
 enum perf_event_type {
 
         /*
+         * If perf_event_attr.sample_id_all is set then all event types will
+         * have the sample_type selected fields related to where/when
+         * (identity) an event took place (TID, TIME, ID, CPU, STREAM_ID)
+         * described in PERF_RECORD_SAMPLE below, it will be stashed just after
+         * the perf_event_header and the fields already present for the existing
+         * fields, i.e. at the end of the payload. That way a newer perf.data
+         * file will be supported by older perf tools, with these new optional
+         * fields being ignored.
+         *
          * The MMAP events record the PROT_EXEC mappings so that we can
          * correlate userspace IPs to code. They have the following structure:
          *