perf record: Read from overwritable ring buffer

Drive the evlist->bkw_mmap_state state machine during draining and when
SIGUSR2 is received. Read the backward ring buffer in record__mmap_read_all.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468485287-33422-12-git-send-email-wangnan0@huawei.com
Signed-off-by: He Kuang <hekuang@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d4f15e76c98a3b91add424a1173ebf61ea7a964c..b87070b1f492b82e7cd15dc83bd53f947ff3bb90 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -555,7 +555,7 @@ static int record__mmap_read_all(struct record *rec)
        if (err)
                return err;
 
-       return err;
+       return record__mmap_read_evlist(rec, rec->evlist, true);
 }
 
 static void record__init_features(struct record *rec)
@@ -953,6 +953,17 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
        for (;;) {
                unsigned long long hits = rec->samples;
 
+               /*
+                * rec->evlist->bkw_mmap_state is possible to be
+                * BKW_MMAP_EMPTY here: when done == true and
+                * hits != rec->samples in previous round.
+                *
+                * perf_evlist__toggle_bkw_mmap ensure we never
+                * convert BKW_MMAP_EMPTY to BKW_MMAP_DATA_PENDING.
+                */
+               if (trigger_is_hit(&switch_output_trigger) || done || draining)
+                       perf_evlist__toggle_bkw_mmap(rec->evlist, BKW_MMAP_DATA_PENDING);
+
                if (record__mmap_read_all(rec) < 0) {
                        trigger_error(&auxtrace_snapshot_trigger);
                        trigger_error(&switch_output_trigger);
@@ -972,8 +983,26 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
                }
 
                if (trigger_is_hit(&switch_output_trigger)) {
+                       /*
+                        * If switch_output_trigger is hit, the data in
+                        * overwritable ring buffer should have been collected,
+                        * so bkw_mmap_state should be set to BKW_MMAP_EMPTY.
+                        *
+                        * If SIGUSR2 raise after or during record__mmap_read_all(),
+                        * record__mmap_read_all() didn't collect data from
+                        * overwritable ring buffer. Read again.
+                        */
+                       if (rec->evlist->bkw_mmap_state == BKW_MMAP_RUNNING)
+                               continue;
                        trigger_ready(&switch_output_trigger);
 
+                       /*
+                        * Reenable events in overwrite ring buffer after
+                        * record__mmap_read_all(): we should have collected
+                        * data from it.
+                        */
+                       perf_evlist__toggle_bkw_mmap(rec->evlist, BKW_MMAP_RUNNING);
+
                        if (!quiet)
                                fprintf(stderr, "[ perf record: dump data: Woken up %ld times ]\n",
                                        waking);