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Subject[patch 07/10] perf_event_open.2: 4.1 add 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>

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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