@@ -680,14 +680,14 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
}
static union perf_event *
-__perf_evlist__mmap_read(struct perf_mmap *md, bool overwrite, u64 head,
- u64 old, u64 *prev)
+__perf_evlist__mmap_read(struct perf_mmap *md, bool check_messup,
+ u64 head, u64 old, u64 *prev)
{
unsigned char *data = md->base + page_size;
union perf_event *event = NULL;
int diff = head - old;
- if (overwrite) {
+ if (check_messup) {
/*
* If we're further behind than half the buffer, there's a chance
* the writer will bite our tail and mess up the samples under us.
@@ -766,6 +766,45 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
old, &md->prev);
}
+union perf_event *
+perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
+{
+ struct perf_mmap *md = &evlist->mmap[idx];
+ u64 head, end;
+ u64 start = md->prev;
+
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!atomic_read(&md->refcnt))
+ return NULL;
+
+ /* NOTE: head is negative in this case */
+ head = perf_mmap__read_head(md);
+
+ if (!head)
+ return NULL;
+
+ end = head + md->mask + 1;
+
+ if ((end - head) > -head)
+ end = 0;
+
+ return __perf_evlist__mmap_read(md, false, end, start, &md->prev);
+}
+
+void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx)
+{
+ struct perf_mmap *md = &evlist->mmap[idx];
+ u64 head;
+
+ if (!atomic_read(&md->refcnt))
+ return;
+
+ head = perf_mmap__read_head(md);
+ md->prev = head;
+}
+
static bool perf_mmap__empty(struct perf_mmap *md)
{
return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
@@ -118,6 +118,10 @@ struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id);
union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx);
+union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist,
+ int idx);
+void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx);
+
void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx);
int perf_evlist__open(struct perf_evlist *evlist);
perf_evlist__mmap_read_backward() is introduced for reading backward ring buffer. Different from reading forward, before reading caller needs to call perf_evlist__mmap_read_catchup() first. Backward ring buffer should be read from 'head' pointer, not '0'. perf_evlist__mmap_read_catchup() saves 'head' to 'md->prev', then use it to remember the start position after each reading. Signed-off-by: Wang Nan <wangnan0@huawei.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Zefan Li <lizefan@huawei.com> Cc: pi3orama@163.com --- tools/perf/util/evlist.c | 45 ++++++++++++++++++++++++++++++++++++++++++--- tools/perf/util/evlist.h | 4 ++++ 2 files changed, 46 insertions(+), 3 deletions(-) -- 1.8.3.4