perf evlist: Setup backward mmap state machine

Introduce a bkw_mmap_state state machine to evlist:

                     .________________(forbid)_____________.
                     |                                     V
 NOTREADY --(0)--> RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
                     ^  ^              |   ^               |
                     |  |__(forbid)____/   |___(forbid)___/|
                     |                                     |
                      \_________________(3)_______________/

 NOTREADY     : Backward ring buffers are not ready
 RUNNING      : Backward ring buffers are recording
 DATA_PENDING : We are required to collect data from backward ring buffers
 EMPTY        : We have collected data from backward ring buffers.

 (0): Setup backward ring buffer
 (1): Pause ring buffers for reading
 (2): Read from ring buffers
 (3): Resume ring buffers for recording

We can't avoid this complexity. Since we deliberately drop records from
overwritable ring buffer, there's no way for us to check remaining from
ring buffer itself (by checking head and old pointers). Therefore, we
need DATA_PENDING and EMPTY state to help us recording what we have done
to the ring buffer.

In record__mmap_read_evlist(), drive this state machine from DATA_PENDING
to EMPTY.

In perf_evlist__mmap_per_evsel(), drive this state machine from NOTREADY
to RUNNING when creating backward mmap.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: He Kuang <hekuang@huawei.com>
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/1468485287-33422-11-git-send-email-wangnan0@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 dbcb223043986959c082fcb3fdb31392aa20a4b5..d4f15e76c98a3b91add424a1173ebf61ea7a964c 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -513,6 +513,9 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
        if (!maps)
                return 0;
 
+       if (backward && evlist->bkw_mmap_state != BKW_MMAP_DATA_PENDING)
+               return 0;
+
        for (i = 0; i < evlist->nr_mmaps; i++) {
                struct auxtrace_mmap *mm = &maps[i].auxtrace_mmap;
 
@@ -538,6 +541,8 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
        if (bytes_written != rec->bytes_written)
                rc = record__write(rec, &finished_round_event, sizeof(finished_round_event));
 
+       if (backward)
+               perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_EMPTY);
 out:
        return rc;
 }

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 5beb44faa71d2a88ee0fe04801b9150a8a3354f6..93ab66415f517c49d92e0bc7e32bcbb4dd9f42ba 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -15,6 +15,7 @@
 #include "evlist.h"
 #include "evsel.h"
 #include "debug.h"
+#include "asm/bug.h"
 #include <unistd.h>
 
 #include "parse-events.h"
@@ -44,6 +45,7 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,
        perf_evlist__set_maps(evlist, cpus, threads);
        fdarray__init(&evlist->pollfd, 64);
        evlist->workload.pid = -1;
+       evlist->bkw_mmap_state = BKW_MMAP_NOTREADY;
 }
 
 struct perf_evlist *perf_evlist__new(void)
@@ -1068,6 +1070,8 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
                                if (!maps)
                                        return -1;
                                evlist->backward_mmap = maps;
+                               if (evlist->bkw_mmap_state == BKW_MMAP_NOTREADY)
+                                       perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_RUNNING);
                        }
                }
 
@@ -1972,3 +1976,61 @@ perf_evlist__find_evsel_by_str(struct perf_evlist *evlist,
 
        return NULL;
 }
+
+void perf_evlist__toggle_bkw_mmap(struct perf_evlist *evlist,
+                                 enum bkw_mmap_state state)
+{
+       enum bkw_mmap_state old_state = evlist->bkw_mmap_state;
+       enum action {
+               NONE,
+               PAUSE,
+               RESUME,
+       } action = NONE;
+
+       if (!evlist->backward_mmap)
+               return;
+
+       switch (old_state) {
+       case BKW_MMAP_NOTREADY: {
+               if (state != BKW_MMAP_RUNNING)
+                       goto state_err;;
+               break;
+       }
+       case BKW_MMAP_RUNNING: {
+               if (state != BKW_MMAP_DATA_PENDING)
+                       goto state_err;
+               action = PAUSE;
+               break;
+       }
+       case BKW_MMAP_DATA_PENDING: {
+               if (state != BKW_MMAP_EMPTY)
+                       goto state_err;
+               break;
+       }
+       case BKW_MMAP_EMPTY: {
+               if (state != BKW_MMAP_RUNNING)
+                       goto state_err;
+               action = RESUME;
+               break;
+       }
+       default:
+               WARN_ONCE(1, "Shouldn't get there\n");
+       }
+
+       evlist->bkw_mmap_state = state;
+
+       switch (action) {
+       case PAUSE:
+               perf_evlist__pause(evlist);
+               break;
+       case RESUME:
+               perf_evlist__resume(evlist);
+               break;
+       case NONE:
+       default:
+               break;
+       }
+
+state_err:
+       return;
+}

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 6a3d9bdda4bb7ece4e024b51534b042d104948dc..20faaab1941c67c9f45a60bf0d27e47c70cac447 100644 (file)
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -41,6 +41,34 @@ perf_mmap__mmap_len(struct perf_mmap *map)
        return map->mask + 1 + page_size;
 }
 
+/*
+ * State machine of bkw_mmap_state:
+ *
+ *                     .________________(forbid)_____________.
+ *                     |                                     V
+ * NOTREADY --(0)--> RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
+ *                     ^  ^              |   ^               |
+ *                     |  |__(forbid)____/   |___(forbid)___/|
+ *                     |                                     |
+ *                      \_________________(3)_______________/
+ *
+ * NOTREADY     : Backward ring buffers are not ready
+ * RUNNING      : Backward ring buffers are recording
+ * DATA_PENDING : We are required to collect data from backward ring buffers
+ * EMPTY        : We have collected data from backward ring buffers.
+ *
+ * (0): Setup backward ring buffer
+ * (1): Pause ring buffers for reading
+ * (2): Read from ring buffers
+ * (3): Resume ring buffers for recording
+ */
+enum bkw_mmap_state {
+       BKW_MMAP_NOTREADY,
+       BKW_MMAP_RUNNING,
+       BKW_MMAP_DATA_PENDING,
+       BKW_MMAP_EMPTY,
+};
+
 struct perf_evlist {
        struct list_head entries;
        struct hlist_head heads[PERF_EVLIST__HLIST_SIZE];
@@ -54,6 +82,7 @@ struct perf_evlist {
        int              id_pos;
        int              is_pos;
        u64              combined_sample_type;
+       enum bkw_mmap_state bkw_mmap_state;
        struct {
                int     cork_fd;
                pid_t   pid;
@@ -135,6 +164,8 @@ struct perf_evsel *perf_evlist__id2evsel_strict(struct perf_evlist *evlist,
 
 struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id);
 
+void perf_evlist__toggle_bkw_mmap(struct perf_evlist *evlist, enum bkw_mmap_state state);
+
 union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_messup);
 union perf_event *perf_mmap__read_backward(struct perf_mmap *map);