From: Kan Liang <kan.li...@intel.com>
The perf_evlist__mmap_read only support forward mode. It needs a common
function to support both forward and backward mode.
The perf_evlist__mmap_read_backward is buggy.
Introduce a new mmap read interface to support both forward and backward
mode. It can read event one by one from the specific range of ring
buffer.
The standard process to mmap__read event would be as below.
perf_mmap__read_init
while (event = perf_mmap__read_event) {
//process the event
perf_mmap__consume
}
perf_mmap__read_done
The following patches will use it to replace the old interfaces.
Signed-off-by: Kan Liang <kan.li...@intel.com>
---
tools/perf/util/evlist.c | 41 +++++++++++++++++++++++++++++++++++++++++
tools/perf/util/evlist.h | 2 ++
2 files changed, 43 insertions(+)
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7d23cf5..b36211e 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -897,6 +897,47 @@ perf_mmap__read(struct perf_mmap *md, bool check_messup,
u64 start,
return event;
}
+/*
+ * Read the first event in the specified range of the ring buffer.
+ * Used by most of the perf tools and tests
+ */
+union perf_event *
+perf_mmap__read_event(struct perf_mmap_read *read)
+{
+ struct perf_mmap *md = read->md;
+ union perf_event *event;
+
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!refcount_read(&md->refcnt))
+ return NULL;
+
+ /* In backward, the ringbuffer is already paused. */
+ if (!read->backward) {
+ read->end = perf_mmap__read_head(md);
+ if (!read->end)
+ return NULL;
+ }
+
+ event = perf_mmap__read(md, !read->backward && read->overwrite,
+ read->start, read->end, &md->prev);
+ read->start = md->prev;
+ return event;
+}
+
+/*
+ * Mandatory for backward
+ * The direction of backward mmap__read_event is from head to tail.
+ * The last mmap__read_event will set tail to md->prev.
+ * Need to correct the md->prev.
+ */
+void
+perf_mmap__read_done(struct perf_mmap_read *read)
+{
+ read->md->prev = read->head;
+}
+
union perf_event *perf_mmap__read_forward(struct perf_mmap *md, bool
check_messup)
{
u64 head;
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 1ce4857..53baf26 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -207,6 +207,8 @@ int perf_mmap__read_init(struct perf_mmap *md, struct
perf_mmap_read *read,
bool overwrite, bool backward);
int perf_mmap__read_to_file(struct perf_mmap_read *read,
struct perf_data_file *file);
+union perf_event *perf_mmap__read_event(struct perf_mmap_read *read);
+void perf_mmap__read_done(struct perf_mmap_read *read);
int perf_evlist__open(struct perf_evlist *evlist);
void perf_evlist__close(struct perf_evlist *evlist);
--
2.5.5
