perf: Differentiate exec() and non-exec() comm events
perf tools like 'perf report' can aggregate samples by comm strings,
which generally works. However, there are other potential use-cases.
For example, to pair up 'calls' with 'returns' accurately (from branch
events like Intel BTS) it is necessary to identify whether the process
has exec'd. Although a comm event is generated when an 'exec' happens
it is also generated whenever the comm string is changed on a whim
(e.g. by prctl PR_SET_NAME). This patch adds a flag to the comm event
to differentiate one case from the other.
In order to determine whether the kernel supports the new flag, a
selection bit named 'exec' is added to struct perf_event_attr. The
bit does nothing but will cause perf_event_open() to fail if the bit
is set on kernels that do not have it defined.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/537D9EBE.7030806@intel.com
Cc: Paul Mackerras <paulus@samba.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index d9cd853..5312fae 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -302,8 +302,8 @@
exclude_callchain_kernel : 1, /* exclude kernel callchains */
exclude_callchain_user : 1, /* exclude user callchains */
mmap2 : 1, /* include mmap with inode data */
-
- __reserved_1 : 40;
+ comm_exec : 1, /* flag comm events that are due to an exec */
+ __reserved_1 : 39;
union {
__u32 wakeup_events; /* wakeup every n events */
@@ -502,7 +502,12 @@
#define PERF_RECORD_MISC_GUEST_KERNEL (4 << 0)
#define PERF_RECORD_MISC_GUEST_USER (5 << 0)
+/*
+ * PERF_RECORD_MISC_MMAP_DATA and PERF_RECORD_MISC_COMM_EXEC are used on
+ * different events so can reuse the same bit position.
+ */
#define PERF_RECORD_MISC_MMAP_DATA (1 << 13)
+#define PERF_RECORD_MISC_COMM_EXEC (1 << 13)
/*
* Indicates that the content of PERF_SAMPLE_IP points to
* the actual instruction that triggered the event. See also