[patch] perf_event_open.2: PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT

From: Vince Weaver
Date: Mon Oct 17 2016 - 10:50:57 EST

Linux 4.2 reserved a new bit from the misc field in the perf_event_open
mmap sample buffer:

Despite being reserved in the public include/uapi/linux/perf_event.h
header file, this bit is never set by the kernel, rather it is used
internally by the userspace "perf" utility to indicate that when
attempting to parse all of the /proc/xxx/maps files for the sample
it ended up taking too long so the scan was aborted.

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

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index fa8b1bd..59ad289 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -1822,6 +1822,14 @@ See also
.BR PERF_RECORD_MISC_EXT_RESERVED " (since Linux 2.6.35)"
.\" commit 1676b8a077c352085d52578fb4f29350b58b6e74
This indicates there is extended data available (currently not used).
+.\" commit 930e6fcd2bcce9bcd9d4aa7e755678d33f3fe6f4
+This bit is not set by the kernel.
+It is reserved for the userspace perf utility to indicate that
+.I /proc/xxx/maps
+parsing was taking too long and stopped and thus the mmap
+records may be truncated.
.I type