Commit-ID:  7257bb0efc6ab4b3a16e1c5154f70d30551e3a7b
Gitweb:     https://git.kernel.org/tip/7257bb0efc6ab4b3a16e1c5154f70d30551e3a7b
Author:     Kan Liang <kan.li...@intel.com>
AuthorDate: Thu, 18 Jan 2018 13:26:23 -0800
Committer:  Arnaldo Carvalho de Melo <a...@redhat.com>
CommitDate: Tue, 6 Feb 2018 10:11:50 -0300

perf mmap: Introduce perf_mmap__read_event()

Except for 'perf record', the other perf tools read events one by one
from the ring buffer using 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 reads 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.li...@intel.com>
Acked-by: Jiri Olsa <jo...@kernel.org>
Cc: Andi Kleen <a...@linux.intel.com>
Cc: Jin Yao <yao....@linux.intel.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Wang Nan <wangn...@huawei.com>
Link: 
http://lkml.kernel.org/r/1516310792-208685-9-git-send-email-kan.li...@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.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 4f59eae..f804926 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 95549d4..2871854 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));
 

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