[PATCH 41/46] perf tools: Add API to pause a channel

Wang Nan
2016-02-26T09:34:37Z

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 c72905d..b5da393 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