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Subject[PATCH V4 06/15] perf mmap: introduce perf_mmap__read_event()
Date
From: Kan Liang <kan.liang@intel.com>

Except perf record, other perf tools read events one by one from ring
buffer by perf_mmap__read_forward(). But it only supports non-overwrite
mode.

Introduce perf_mmap__read_event() to support both non-overwrite and
overwrite mode.

Usage:
perf_mmap__read_init()
while(event = perf_mmap__read_event()) {
//process the event
perf_mmap__consume()
}
perf_mmap__read_done()

It cannot use perf_mmap__read_backward(). Because it always read the
stale buffer which is already processed. Furthermore, the forward and
backward concepts have been removed. The perf_mmap__read_backward() will
be replaced and discarded later.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
tools/perf/util/mmap.c | 39 +++++++++++++++++++++++++++++++++++++++
tools/perf/util/mmap.h | 4 ++++
2 files changed, 43 insertions(+)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 2291160..de50c71 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -113,6 +113,45 @@ union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
return perf_mmap__read(map, &map->prev, end);
}

+/*
+ * Read event from ring buffer one by one.
+ * Return one event for each call.
+ *
+ * Usage:
+ * perf_mmap__read_init()
+ * while(event = perf_mmap__read_event()) {
+ * //process the event
+ * perf_mmap__consume()
+ * }
+ * perf_mmap__read_done()
+ */
+union perf_event *perf_mmap__read_event(struct perf_mmap *map,
+ bool overwrite,
+ u64 *startp, u64 end)
+{
+ union perf_event *event;
+
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!refcount_read(&map->refcnt))
+ return NULL;
+
+ if (startp == NULL)
+ return NULL;
+
+ /* non-overwirte doesn't pause the ringbuffer */
+ if (!overwrite)
+ end = perf_mmap__read_head(map);
+
+ event = perf_mmap__read(map, startp, end);
+
+ if (!overwrite)
+ map->prev = *startp;
+
+ return event;
+}
+
void perf_mmap__read_catchup(struct perf_mmap *map)
{
u64 head;
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index 4434cc5..29d7c5d 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -89,6 +89,10 @@ static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
union perf_event *perf_mmap__read_forward(struct perf_mmap *map);
union perf_event *perf_mmap__read_backward(struct perf_mmap *map);

+union perf_event *perf_mmap__read_event(struct perf_mmap *map,
+ bool overwrite,
+ u64 *startp, u64 end);
+
int perf_mmap__push(struct perf_mmap *md, bool backward,
void *to, int push(void *to, void *buf, size_t size));

--
2.5.5
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