[RFC][PATCH 15/21] tracing: Add usecs modifier for hist trigger timestamps

Tom Zanussi
2017-02-08T17:29:44Z

Appending .usecs onto a common_timestamp field will cause the
timestamp value to be in microseconds instead of the default
nanoseconds. A typical latency histogram using usecs would look like
this:

# echo 'hist:keys=pid,prio:ts0=common_timestamp.usecs ...
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-ts0 ...

This also adds an external trace_clock_in_ns() to trace.c for the
timestamp conversion.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
kernel/trace/trace.c | 8 ++++++++
kernel/trace/trace.h | 2 ++
kernel/trace/trace_events_hist.c | 33 ++++++++++++++++++++++++---------
3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 78dff2f..f2a3b9c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1172,6 +1172,14 @@ unsigned long nsecs_to_usecs(unsigned long nsecs)
ARCH_TRACE_CLOCKS
};

+bool trace_clock_in_ns(struct trace_array *tr)
+{
+ if (trace_clocks[tr->clock_id].in_ns)
+ return true;
+
+ return false;
+}
+
/*
* trace_parser_get_init - gets the buffer for trace parser
*/
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f2af21b..1d0991b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -280,6 +280,8 @@ enum {

extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);

+extern bool trace_clock_in_ns(struct trace_array *tr);
+
/*
* The global tracer (top) should be the first trace array added,
* but we check the flag anyway.
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c0a2ce8..13d67d3 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -163,14 +163,6 @@ static u64 hist_field_log2(struct hist_field *hist_field,
return (u64) ilog2(roundup_pow_of_two(val));
}

-static u64 hist_field_timestamp(struct hist_field *hist_field,
- struct tracing_map_elt *elt,
- struct ring_buffer_event *rbe,
- void *event)
-{
- return ring_buffer_event_time_stamp(rbe);
-}
-
#define DEFINE_HIST_FIELD_FN(type) \
static u64 hist_field_##type(struct hist_field *hist_field, \
struct tracing_map_elt *elt, \
@@ -223,6 +215,7 @@ enum hist_field_flags {
HIST_FIELD_FL_VAR_REF = 4096,
HIST_FIELD_FL_EXPR = 8192,
HIST_FIELD_FL_TIMESTAMP = 16384,
+ HIST_FIELD_FL_TIMESTAMP_USECS = 32768,
};

struct hist_trigger_attrs {
@@ -235,6 +228,7 @@ struct hist_trigger_attrs {
bool pause;
bool cont;
bool clear;
+ bool ts_in_usecs;
unsigned int map_bits;
};

@@ -255,6 +249,22 @@ struct hist_trigger_data {
bool enable_timestamps;
};

+static u64 hist_field_timestamp(struct hist_field *hist_field,
+ struct tracing_map_elt *elt,
+ struct ring_buffer_event *rbe,
+ void *event)
+{
+ struct hist_trigger_data *hist_data = elt->map->private_data;
+ struct trace_array *tr = hist_data->event_file->tr;
+
+ u64 ts = ring_buffer_event_time_stamp(rbe);
+
+ if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))
+ ts = ns2usecs(ts);
+
+ return ts;
+}
+
static LIST_HEAD(hist_var_list);

struct hist_var_data {
@@ -620,7 +630,6 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)

while (trigger_str) {
char *str = strsep(&trigger_str, ":");
-
if (strchr(str, '=')) {
ret = parse_assignment(str, attrs);
if (ret)
@@ -948,6 +957,8 @@ static struct hist_field *parse_var_ref(char *var_name)
*flags |= HIST_FIELD_FL_SYSCALL;
else if (strcmp(field_str, "log2") == 0)
*flags |= HIST_FIELD_FL_LOG2;
+ else if (strcmp(field_str, "usecs") == 0)
+ *flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
else
return ERR_PTR(-EINVAL);
}
@@ -955,6 +966,8 @@ static struct hist_field *parse_var_ref(char *var_name)
if (strcmp(field_name, "common_timestamp") == 0) {
*flags |= HIST_FIELD_FL_TIMESTAMP;
hist_data->enable_timestamps = true;
+ if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+ hist_data->attrs->ts_in_usecs = true;
} else {
field = trace_find_event_field(file->event_call, field_name);
if (!field)
@@ -1949,6 +1962,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
flags_str = "syscall";
else if (hist_field->flags & HIST_FIELD_FL_LOG2)
flags_str = "log2";
+ else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+ flags_str = "usecs";

return flags_str;
}
--
1.9.3