linux-kernel - [patch 07/11] perf_event_open.2: 4.1 add AUX_FLAG

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Message-ID: <alpine.DEB.2.20.1507231313130.3742@vincent-weaver-1.umelst.maine.edu>
Date:	Thu, 23 Jul 2015 13:13:52 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
cc:	linux-man@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Kaixu Xia <kaixu.xia@...aro.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Robert Richter <rric@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, adrian.hunter@...el.com,
	kan.liang@...el.com, markus.t.metzger@...el.com,
	mathieu.poirier@...aro.org, Vince Weaver <vincent.weaver@...ne.edu>
Subject: [patch 07/11] 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@...ux.intel.com>

	perf: Support overwrite mode for the AUX area

	Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
	Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
	Cc: Borislav Petkov <bp@...en8.de>
	Cc: Frederic Weisbecker <fweisbec@...il.com>
	Cc: H. Peter Anvin <hpa@...or.com>
	Cc: Kaixu Xia <kaixu.xia@...aro.org>
	Cc: Linus Torvalds <torvalds@...ux-foundation.org>
	Cc: Mike Galbraith <efault@....de>
	Cc: Paul Mackerras <paulus@...ba.org>
	Cc: Robert Richter <rric@...nel.org>
	Cc: Stephane Eranian <eranian@...gle.com>
	Cc: Thomas Gleixner <tglx@...utronix.de>
	Cc: acme@...radead.org
	Cc: adrian.hunter@...el.com
	Cc: kan.liang@...el.com
	Cc: markus.t.metzger@...el.com
	Cc: mathieu.poirier@...aro.org
	Link: http://lkml.kernel.org/r/1421237903-181015-9-git-send-email-alexander.shishkin@linux.intel.com
	Signed-off-by: Ingo Molnar <mingo@...nel.org>

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

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index dfb0b64..238eb62 100644
--- 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
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