[PATCH v5 5/8] perf record: Toggle overwrite ring buffer for reading

[Wang Nan]

overwrite_evt_state is introduced to reflect the state of overwritable
ring buffers. It is a state machine with 3 states:

 RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
^  ^ |
|  |___(disallow)___/|
||
 \_(3)__/

 RUNNING  : Overwritable ring buffers are recording
 DATA_PENDING : We are required to collect overwritable ring buffers
 EMPTY: We have collected data from those ring buffers.

 (1): Pause ring buffers for reading
 (2): Read from ring buffers
 (3): Resume ring buffers for recording

We can't avoid this complexity. Because we deliberately drop records from
overwritable ring buffer, we can't detect remaining data by checking head
and old pointers. Therefore, DATA_PENDING state is mandatory.

Signed-off-by: Wang Nan 
Signed-off-by: He Kuang 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Masami Hiramatsu 
Cc: Namhyung Kim 
Cc: Zefan Li 
Cc: pi3or...@163.com
---
 tools/perf/builtin-record.c | 146 +---
 1 file changed, 136 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e7be4e1..d5bb947 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -42,6 +42,28 @@
 #include 
 #include 
 
+/*
+ * State machine of overwrite_evt_state:
+ *
+ * RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
+ *^  ^ |
+ *|  |___(disallow)___/|
+ *||
+ * \_(3)__/
+ *
+ * RUNNING  : Overwritable ring buffers are recording
+ * DATA_PENDING : We are required to collect overwritable ring buffers
+ * EMPTY: We have collected data from those ring buffers.
+ *
+ * (1): Pause ring buffers for reading
+ * (2): Read from ring buffers
+ * (3): Resume ring buffers for recording
+ */
+enum overwrite_evt_state {
+   OVERWRITE_EVT_RUNNING,
+   OVERWRITE_EVT_DATA_PENDING,
+   OVERWRITE_EVT_EMPTY,
+};
 
 struct record {
struct perf_tooltool;
@@ -61,6 +83,7 @@ struct record {
boolbuildid_all;
booltimestamp_filename;
boolswitch_output;
+   enum overwrite_evt_state overwrite_evt_state;
unsigned long long  samples;
 };
 
@@ -132,9 +155,9 @@ rb_find_range(struct perf_evlist *evlist,
return backward_rb_find_range(data, mask, head, start, end);
 }
 
-static int record__mmap_read(struct record *rec, int idx)
+static int record__mmap_read(struct record *rec, struct perf_evlist *evlist, 
int idx)
 {
-   struct perf_mmap *md = >evlist->mmap[idx];
+   struct perf_mmap *md = >mmap[idx];
u64 head = perf_mmap__read_head(md);
u64 old = md->prev;
u64 end = head, start = old;
@@ -143,7 +166,7 @@ static int record__mmap_read(struct record *rec, int idx)
void *buf;
int rc = 0;
 
-   if (rb_find_range(rec->evlist, data, md->mask, head,
+   if (rb_find_range(evlist, data, md->mask, head,
  old, , ))
return -1;
 
@@ -157,7 +180,7 @@ static int record__mmap_read(struct record *rec, int idx)
WARN_ONCE(1, "failed to keep up with mmap data. (warn only 
once)\n");
 
md->prev = head;
-   perf_evlist__mmap_consume(rec->evlist, idx);
+   perf_evlist__mmap_consume(evlist, idx);
return 0;
}
 
@@ -182,7 +205,7 @@ static int record__mmap_read(struct record *rec, int idx)
}
 
md->prev = head;
-   perf_evlist__mmap_consume(rec->evlist, idx);
+   perf_evlist__mmap_consume(evlist, idx);
 out:
return rc;
 }
@@ -468,6 +491,7 @@ try_again:
goto out;
session->evlist = evlist;
perf_session__set_id_hdr_size(session);
+   rec->overwrite_evt_state = OVERWRITE_EVT_RUNNING;
 out:
return rc;
 }
@@ -548,17 +572,72 @@ static struct perf_event_header finished_round_event = {
.type = PERF_RECORD_FINISHED_ROUND,
 };
 
-static int record__mmap_read_all(struct record *rec)
+static void
+record__toggle_overwrite_evsels(struct record *rec,
+   enum overwrite_evt_state state)
+{
+   struct perf_evlist *evlist = rec->overwrite_evlist;
+   enum overwrite_evt_state old_state = rec->overwrite_evt_state;
+   enum action {
+   NONE,
+   PAUSE,
+   RESUME,
+   } action = NONE;
+
+   switch (old_state) {
+   case OVERWRITE_EVT_RUNNING:
+   if (state != OVERWRITE_EVT_RUNNING)
+   action = PAUSE;
+   break;
+   case OVERWRITE_EVT_DATA_PENDING:
+   

[PATCH v5 5/8] perf record: Toggle overwrite ring buffer for reading

[Wang Nan]

overwrite_evt_state is introduced to reflect the state of overwritable
ring buffers. It is a state machine with 3 states:

 RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
^  ^ |
|  |___(disallow)___/|
||
 \_(3)__/

 RUNNING  : Overwritable ring buffers are recording
 DATA_PENDING : We are required to collect overwritable ring buffers
 EMPTY: We have collected data from those ring buffers.

 (1): Pause ring buffers for reading
 (2): Read from ring buffers
 (3): Resume ring buffers for recording

We can't avoid this complexity. Because we deliberately drop records from
overwritable ring buffer, we can't detect remaining data by checking head
and old pointers. Therefore, DATA_PENDING state is mandatory.

Signed-off-by: Wang Nan 
Signed-off-by: He Kuang 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Masami Hiramatsu 
Cc: Namhyung Kim 
Cc: Zefan Li 
Cc: pi3or...@163.com
---
 tools/perf/builtin-record.c | 146 +---
 1 file changed, 136 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e7be4e1..d5bb947 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -42,6 +42,28 @@
 #include 
 #include 
 
+/*
+ * State machine of overwrite_evt_state:
+ *
+ * RUNNING --(1)--> DATA_PENDING --(2)--> EMPTY
+ *^  ^ |
+ *|  |___(disallow)___/|
+ *||
+ * \_(3)__/
+ *
+ * RUNNING  : Overwritable ring buffers are recording
+ * DATA_PENDING : We are required to collect overwritable ring buffers
+ * EMPTY: We have collected data from those ring buffers.
+ *
+ * (1): Pause ring buffers for reading
+ * (2): Read from ring buffers
+ * (3): Resume ring buffers for recording
+ */
+enum overwrite_evt_state {
+   OVERWRITE_EVT_RUNNING,
+   OVERWRITE_EVT_DATA_PENDING,
+   OVERWRITE_EVT_EMPTY,
+};
 
 struct record {
struct perf_tooltool;
@@ -61,6 +83,7 @@ struct record {
boolbuildid_all;
booltimestamp_filename;
boolswitch_output;
+   enum overwrite_evt_state overwrite_evt_state;
unsigned long long  samples;
 };
 
@@ -132,9 +155,9 @@ rb_find_range(struct perf_evlist *evlist,
return backward_rb_find_range(data, mask, head, start, end);
 }
 
-static int record__mmap_read(struct record *rec, int idx)
+static int record__mmap_read(struct record *rec, struct perf_evlist *evlist, 
int idx)
 {
-   struct perf_mmap *md = >evlist->mmap[idx];
+   struct perf_mmap *md = >mmap[idx];
u64 head = perf_mmap__read_head(md);
u64 old = md->prev;
u64 end = head, start = old;
@@ -143,7 +166,7 @@ static int record__mmap_read(struct record *rec, int idx)
void *buf;
int rc = 0;
 
-   if (rb_find_range(rec->evlist, data, md->mask, head,
+   if (rb_find_range(evlist, data, md->mask, head,
  old, , ))
return -1;
 
@@ -157,7 +180,7 @@ static int record__mmap_read(struct record *rec, int idx)
WARN_ONCE(1, "failed to keep up with mmap data. (warn only 
once)\n");
 
md->prev = head;
-   perf_evlist__mmap_consume(rec->evlist, idx);
+   perf_evlist__mmap_consume(evlist, idx);
return 0;
}
 
@@ -182,7 +205,7 @@ static int record__mmap_read(struct record *rec, int idx)
}
 
md->prev = head;
-   perf_evlist__mmap_consume(rec->evlist, idx);
+   perf_evlist__mmap_consume(evlist, idx);
 out:
return rc;
 }
@@ -468,6 +491,7 @@ try_again:
goto out;
session->evlist = evlist;
perf_session__set_id_hdr_size(session);
+   rec->overwrite_evt_state = OVERWRITE_EVT_RUNNING;
 out:
return rc;
 }
@@ -548,17 +572,72 @@ static struct perf_event_header finished_round_event = {
.type = PERF_RECORD_FINISHED_ROUND,
 };
 
-static int record__mmap_read_all(struct record *rec)
+static void
+record__toggle_overwrite_evsels(struct record *rec,
+   enum overwrite_evt_state state)
+{
+   struct perf_evlist *evlist = rec->overwrite_evlist;
+   enum overwrite_evt_state old_state = rec->overwrite_evt_state;
+   enum action {
+   NONE,
+   PAUSE,
+   RESUME,
+   } action = NONE;
+
+   switch (old_state) {
+   case OVERWRITE_EVT_RUNNING:
+   if (state != OVERWRITE_EVT_RUNNING)
+   action = PAUSE;
+   break;
+   case OVERWRITE_EVT_DATA_PENDING:
+   if (state == OVERWRITE_EVT_RUNNING)
+   action = RESUME;
+   break;
+   case OVERWRITE_EVT_EMPTY:
+