2015-04-16 18:12:50

by Vince Weaver

[permalink] [raw]
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 <[email protected]>

perf: Support overwrite mode for the AUX area

Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Kaixu Xia <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <[email protected]>

Signed-off-by: Vince Weaver <[email protected]>

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