linux-kernel - [PATCH 49/54] perf tools: Add API to pause a channel

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Date:	Fri, 5 Feb 2016 14:02:14 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	Alexei Starovoitov <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>
CC:	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <dev@...yps.com>,
	"David S. Miller" <davem@...emloft.net>,
	He Kuang <hekuang@...wei.com>,
	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>, Jiri Olsa <jolsa@...nel.org>,
	Kirill Smelkov <kirr@...edi.com>,
	Li Zefan <lizefan@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, <pi3orama@....com>,
	Wang Nan <wangnan0@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 49/54] perf tools: Add API to pause a channel

perf_evlist__channel_toggle_paused() is introduced to pause/resume a
channel in an evlist. Utilize PERF_EVENT_IOC_PAUSE_OUTPUT ioctl.
Following commits use perf_evlist__channel_toggle_paused() to ensure
overwrite ring buffer is turned off before reading.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Signed-off-by: He Kuang <hekuang@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Zefan Li <lizefan@...wei.com>
Cc: pi3orama@....com
---
 tools/perf/util/evlist.c | 28 ++++++++++++++++++++++++++++
 tools/perf/util/evlist.h |  2 ++
 2 files changed, 30 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index c543024..38e1c3a 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -706,6 +706,34 @@ int perf_evlist__channel_idx(struct perf_evlist *evlist,
 	return 0;
 }
 
+int perf_evlist__channel_toggle_paused(struct perf_evlist *evlist,
+				       int channel, bool pause)
+{
+	int i;
+
+	if (channel >= perf_evlist__channel_nr(evlist))
+		return -E2BIG;
+	if (!evlist->mmap)
+		return -EFAULT;
+	for (i = 0; i < evlist->nr_mmaps; i++) {
+		int n = channel * evlist->nr_mmaps + i;
+		int fd = evlist->mmap[n].fd;
+		int err;
+
+		if (fd < 0)
+			continue;
+		err = ioctl(fd, PERF_EVENT_IOC_PAUSE_OUTPUT,
+			    pause ? 1 : 0);
+		if (err) {
+			err = (errno == 0 ? -EINVAL : -errno);
+			pr_err("Unable to pause output on %d: %s\n",
+			       fd, strerror(-err));
+			return err;
+		}
+	}
+	return 0;
+}
+
 union perf_event *perf_evlist__mmap_read_ex(struct perf_evlist *evlist,
 					    int channel, int idx)
 {
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index bc6d787..c1831a9 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -180,6 +180,8 @@ perf_evlist__get_mmap(struct perf_evlist *evlist,
 	return &evlist->mmap[idx];
 }
 
+int perf_evlist__channel_toggle_paused(struct perf_evlist *evlist,
+				       int channel, bool pause);
 int perf_evlist__open(struct perf_evlist *evlist);
 void perf_evlist__close(struct perf_evlist *evlist);
 
-- 
1.8.3.4