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/util/evlist.c b/tools/perf/util/evlist.c
index 5beb44f..93ab664 100644
--- 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 @@
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 @@
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 @@
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;
+}