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

From: Wang Nan <wangnan0@huawei.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: "Adrian Hunter" <adrian.hunter@intel.com>,
	"Cody P Schafer" <dev@codyps.com>,
	"David S. Miller" <davem@davemloft.net>,
	"He Kuang" <hekuang@huawei.com>,
	"Jérémie Galarneau" <jeremie.galarneau@efficios.com>,
	"Jiri Olsa" <jolsa@kernel.org>,
	"Kirill Smelkov" <kirr@nexedi.com>,
	"Li Zefan" <lizefan@huawei.com>,
	"Masami Hiramatsu" <masami.hiramatsu.pt@hitachi.com>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	pi3orama@163.com, "Wang Nan" <wangnan0@huawei.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 49/54] perf tools: Add API to pause a channel
Date: Fri, 5 Feb 2016 14:02:14 +0000	[thread overview]
Message-ID: <1454680939-24963-50-git-send-email-wangnan0@huawei.com> (raw)
In-Reply-To: <1454680939-24963-1-git-send-email-wangnan0@huawei.com>

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@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.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
