[patch 07/10] perf_event_open.2: 4.1 add AUX_FLAG_OVERWRITE support

[Vince Weaver]

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@xxxxxxxxxxxxxxx>

	perf: Support overwrite mode for the AUX area

	Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
	Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
	Cc: Borislav Petkov <bp@xxxxxxxxx>
	Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
	Cc: H. Peter Anvin <hpa@xxxxxxxxx>
	Cc: Kaixu Xia <kaixu.xia@xxxxxxxxxx>
	Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
	Cc: Mike Galbraith <efault@xxxxxx>
	Cc: Paul Mackerras <paulus@xxxxxxxxx>
	Cc: Robert Richter <rric@xxxxxxxxxx>
	Cc: Stephane Eranian <eranian@xxxxxxxxxx>
	Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
	Cc: acme@xxxxxxxxxxxxx
	Cc: adrian.hunter@xxxxxxxxx
	Cc: kan.liang@xxxxxxxxx
	Cc: markus.t.metzger@xxxxxxxxx
	Cc: mathieu.poirier@xxxxxxxxxx
	Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@xxxxxxxxxxxxxxx
	Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>

Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx>

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -1590,6 +1590,15 @@
 .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
@@ -2372,6 +2381,10 @@
 .B PERF_AUX_FLAG_TRUNCATED
 if set then the data returned was truncated to fix 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
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