[patch] perf_event_open.2: Document the PERF_EVENT_IOC_PAUSE_OUTPUT ioctl

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The PERF_EVENT_IOC_PAUSE_OUTPUT ioctl was introduced in Linux 4.7.

I've have this patch for a long time, I apologize for the delay
in getting it submitted.  I've made some minor changes to the original
patch proposed by Wang Nan.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Reviewed-by: Vince Weaver <vincent.weaver@xxxxxxxxx>

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index d5b2d060d..acd88f181 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -2928,6 +2930,21 @@ The argument is a BPF program file descriptor that was created by
 a previous
 .BR bpf (2)
 system call.
+.TP
+.BR PERF_EVENT_IOC_PAUSE_OUTPUT " (since Linux 4.7)"
+.\" commit 86e7972f690c1017fd086cdfe53d8524e68c661c
+This allows pausing and resuming the event's ring-buffer.
+A paused ring-buffer does not prevent generation of samples,
+but simply discards them.
+The discarded samples are considered lost, and cause a
+.BR PERF_RECORD_LOST
+sample to be generated when possible.
+An overflow signal may still be triggered by the discarded sample
+even though the ring-buffer remains empty.
+.IP
+The argument is an unsigned 32-bit integer.
+A nonzero value pauses the ring-buffer, while a
+zero value resumes the ring-buffer.
 .SS Using prctl(2)
 A process can enable or disable all the event groups that are
 attached to it using the
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