perf_event_open.2: 4.1 adds AUX_FLAG_OVERWRITE support

This manpage patch relates to the addition of the AUX sample flag
AUX_FLAG_OVERWRITE as added in the following commit:

	commit 2023a0d2829e521fe6ad6b9907f3f90bfbf57142
	Author: Alexander Shishkin <alexander.shishkin@linux.intel.com>

	perf: Support overwrite mode for the AUX area

	Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
	Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
	Cc: Borislav Petkov <bp@alien8.de>
	Cc: Frederic Weisbecker <fweisbec@gmail.com>
	Cc: H. Peter Anvin <hpa@zytor.com>
	Cc: Kaixu Xia <kaixu.xia@linaro.org>
	Cc: Linus Torvalds <torvalds@linux-foundation.org>
	Cc: Mike Galbraith <efault@gmx.de>
	Cc: Paul Mackerras <paulus@samba.org>
	Cc: Robert Richter <rric@kernel.org>
	Cc: Stephane Eranian <eranian@google.com>
	Cc: Thomas Gleixner <tglx@linutronix.de>
	Cc: acme@infradead.org
	Cc: adrian.hunter@intel.com
	Cc: kan.liang@intel.com
	Cc: markus.t.metzger@intel.com
	Cc: mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@linux.intel.com
	Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index 858b63356b9ce07278360e6126e9db99973a6f37..6b9d1dc486c7de0ba3c5e70ebfe1de5373ad17aa 100644 (file)
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -1670,6 +1670,15 @@ rlimit as well as the
 .I perf_event_mlock_kb
 allowance.
 
+By default the AUX buffer will be truncated if it will not fit
+in the available space in the ring buffer.
+If the AUX buffer is mapped as a read only buffer, then it will
+operate in ring buffer mode where old data will be overwritten
+by new.
+In overwrite mode it might not be possible to infer where the
+new data began, and it is the consumer's job to disable
+measurement while reading to avoid possible data races.
+
 The
 .IR aux_head " and " aux_tail
 ring buffer pointers have the same behavior and ordering
@@ -2476,6 +2485,10 @@ describes the aux update.
 .B PERF_AUX_FLAG_TRUNCATED
 if set then the data returned was truncated to fit the available
 buffer size.
+.TP
+.B PERF_AUX_FLAG_OVERWRITE
+.\" commit 2023a0d2829e521fe6ad6b9907f3f90bfbf57142
+if set then the data returned has overwritten previous data.
 .RE
 .RE
 .RE