@@ -1666,17 +1666,26 @@ features have been added to the hist trigger support:
underlying ftrace ring buffer. This timestamp is now exposed as a
a synthetic field named 'common_timestamp' which can be used in
histograms as if it were any other event field; it isn't an actual
field in the trace format but rather is a synthesized value that
nonetheless can be used as if it were an actual field. By default
it is in units of nanoseconds; appending '.usecs' to a
common_timestamp field changes the units to microseconds.
-These features are decribed in more detail in the following sections.
+A note on inter-event timestamps: If common_timestamp is used in a
+histogram, the trace buffer is automatically switched over to using
+absolute timestamps and the "global" trace clock, in order to avoid
+bogus timestamp differences with other clocks that aren't coherent
+across CPUs. This can be overridden by specifying one of the other
+trace clocks instead, using the "clock=XXX" hist trigger attribute,
+where XXX is any of the clocks listed in the tracing/trace_clock
+pseudo-file.
+
+These features are described in more detail in the following sections.
2.2.1 Histogram Variables
-------------------------
Variables are simply named locations used for saving and retrieving
values between matching events. A 'matching' event is defined as an
event that has a matching key - if a variable is saved for a histogram
entry corresponding to that key, any subsequent event with a matching
@@ -237,16 +237,17 @@ struct var_defs {
char *expr[TRACING_MAP_VARS_MAX];
};
struct hist_trigger_attrs {
char *keys_str;
char *vals_str;
char *sort_key_str;
char *name;
+ char *clock;
bool pause;
bool cont;
bool clear;
bool ts_in_usecs;
unsigned int map_bits;
char *assignment_str[TRACING_MAP_VARS_MAX];
unsigned int n_assignments;
@@ -1771,16 +1772,17 @@ static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
for (i = 0; i < attrs->n_actions; i++)
kfree(attrs->action_str[i]);
kfree(attrs->name);
kfree(attrs->sort_key_str);
kfree(attrs->keys_str);
kfree(attrs->vals_str);
+ kfree(attrs->clock);
kfree(attrs);
}
static int parse_action(char *str, struct hist_trigger_attrs *attrs)
{
int ret = -EINVAL;
if (attrs->n_actions >= HIST_ACTIONS_MAX)
@@ -1826,16 +1828,29 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
goto out;
}
} else if (strncmp(str, "name=", strlen("name=")) == 0) {
attrs->name = kstrdup(str, GFP_KERNEL);
if (!attrs->name) {
ret = -ENOMEM;
goto out;
}
+ } else if (strncmp(str, "clock=", strlen("clock=")) == 0) {
+ strsep(&str, "=");
+ if (!str) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ str = strstrip(str);
+ attrs->clock = kstrdup(str, GFP_KERNEL);
+ if (!attrs->clock) {
+ ret = -ENOMEM;
+ goto out;
+ }
} else if (strncmp(str, "size=", strlen("size=")) == 0) {
int map_bits = parse_map_size(str);
if (map_bits < 0) {
ret = map_bits;
goto out;
}
attrs->map_bits = map_bits;
@@ -1890,16 +1905,24 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
}
}
if (!attrs->keys_str) {
ret = -EINVAL;
goto free;
}
+ if (!attrs->clock) {
+ attrs->clock = kstrdup("global", GFP_KERNEL);
+ if (!attrs->clock) {
+ ret = -ENOMEM;
+ goto free;
+ }
+ }
+
return attrs;
free:
destroy_hist_trigger_attrs(attrs);
return ERR_PTR(ret);
}
static inline void save_comm(char *comm, struct task_struct *task)
@@ -4929,16 +4952,18 @@ static int event_hist_trigger_print(struct seq_file *m,
idx += hist_data->n_vars;
hist_field_print(m, hist_data->fields[idx]);
}
if (sort_key->descending)
seq_puts(m, ".descending");
}
seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
+ if (hist_data->enable_timestamps)
+ seq_printf(m, ":clock=%s", hist_data->attrs->clock);
print_actions_spec(m, hist_data);
if (data->filter_str)
seq_printf(m, " if %s", data->filter_str);
if (data->paused)
seq_puts(m, " [paused]");
@@ -5196,32 +5221,43 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
ret = -ENOENT;
goto out;
}
if (hist_data->attrs->pause)
data->paused = true;
if (named_data) {
- destroy_hist_data(data->private_data);
data->private_data = named_data->private_data;
set_named_trigger_data(data, named_data);
data->ops = &event_hist_trigger_named_ops;
}
if (data->ops->init) {
ret = data->ops->init(data->ops, data);
if (ret < 0)
goto out;
}
- ret++;
+ if (hist_data->enable_timestamps) {
+ char *clock = hist_data->attrs->clock;
+
+ ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
+ if (ret) {
+ hist_err("Couldn't set trace_clock: ", clock);
+ goto out;
+ }
- if (hist_data->enable_timestamps)
tracing_set_time_stamp_abs(file->tr, true);
+ }
+
+ if (named_data)
+ destroy_hist_data(hist_data);
+
+ ret++;
out:
return ret;
}
static int hist_trigger_enable(struct event_trigger_data *data,
struct trace_event_file *file)
{
int ret = 0;