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tracing: Add alternative synthetic event trace action syntax

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Add a 'trace(synthetic_event_name, params)' alternative to
synthetic_event_name(params).

Currently, the syntax used for generating synthetic events is to
invoke synthetic_event_name(params) i.e. use the synthetic event name
as a function call.

Users requested a new form that more explicitly shows that the
synthetic event is in effect being traced.  In this version, a new
'trace()' keyword is used, and the synthetic event name is passed in
as the first argument.

In addition, for the sake of consistency with other actions, change
the documention to emphasize the trace() form over the function-call
form, which remains documented as equivalent.

Link: http://lkml.kernel.org/r/d082773e50232a001480cf837679a1e01c1a2eb7.1550100284.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2019-02-13 17:42:50 -06:00 committed by Steven Rostedt (VMware)
parent ff0d35e2e1
commit e91eefd731
3 changed files with 75 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
Documentation/trace/histogram.rst
View File

@ -1873,31 +1873,45 @@ The available handlers are:
The available actions are:
- <synthetic_event_name>(param list) - generate synthetic event
- trace(<synthetic_event_name>,param list) - generate synthetic event
- save(field,...) - save current event fields
- snapshot() - snapshot the trace buffer
The following commonly-used handler.action pairs are available:
- onmatch(matching.event).<synthetic_event_name>(param list)
- onmatch(matching.event).trace(<synthetic_event_name>,param list)
The 'onmatch(matching.event).<synthetic_event_name>(params)' hist
trigger action is invoked whenever an event matches and the
histogram entry would be added or updated. It causes the named
synthetic event to be generated with the values given in the
The 'onmatch(matching.event).trace(<synthetic_event_name>,param
list)' hist trigger action is invoked whenever an event matches
and the histogram entry would be added or updated. It causes the
named synthetic event to be generated with the values given in the
'param list'. The result is the generation of a synthetic event
that consists of the values contained in those variables at the
time the invoking event was hit.
time the invoking event was hit. For example, if the synthetic
event name is 'wakeup_latency', a wakeup_latency event is
generated using onmatch(event).trace(wakeup_latency,arg1,arg2).
The 'param list' consists of one or more parameters which may be
either variables or fields defined on either the 'matching.event'
or the target event. The variables or fields specified in the
param list may be either fully-qualified or unqualified. If a
variable is specified as unqualified, it must be unique between
the two events. A field name used as a param can be unqualified
if it refers to the target event, but must be fully qualified if
it refers to the matching event. A fully-qualified name is of the
form 'system.event_name.$var_name' or 'system.event_name.field'.
There is also an equivalent alternative form available for
generating synthetic events. In this form, the synthetic event
name is used as if it were a function name. For example, using
the 'wakeup_latency' synthetic event name again, the
wakeup_latency event would be generated by invoking it as if it
were a function call, with the event field values passed in as
arguments: onmatch(event).wakeup_latency(arg1,arg2). The syntax
for this form is:
onmatch(matching.event).<synthetic_event_name>(param list)
In either case, the 'param list' consists of one or more
parameters which may be either variables or fields defined on
either the 'matching.event' or the target event. The variables or
fields specified in the param list may be either fully-qualified
or unqualified. If a variable is specified as unqualified, it
must be unique between the two events. A field name used as a
param can be unqualified if it refers to the target event, but
must be fully qualified if it refers to the matching event. A
fully-qualified name is of the form 'system.event_name.$var_name'
or 'system.event_name.field'.
The 'matching.event' specification is simply the fully qualified
event name of the event that matches the target event for the
@ -1928,6 +1942,12 @@ The following commonly-used handler.action pairs are available:
wakeup_new_test($testpid) if comm=="cyclictest"' >> \
/sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
Or, equivalently, using the 'trace' keyword syntax:
# echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\
trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \
/sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
Creating and displaying a histogram based on those events is now
just a matter of using the fields and new synthetic event in the
tracing/events/synthetic directory, as usual::

2
kernel/trace/trace.c
View File

@ -4918,7 +4918,7 @@ static const char readme_msg[] =
"\t onmax(var) - invoke if var exceeds current max\n"
"\t onchange(var) - invoke action if var changes\n\n"
"\t The available actions are:\n\n"
"\t <synthetic_event>(param list) - generate synthetic event\n"
"\t trace(<synthetic_event>,param list) - generate synthetic event\n"
"\t save(field,...) - save current event fields\n"
#ifdef CONFIG_TRACER_SNAPSHOT
"\t snapshot() - snapshot the trace buffer\n"

42
kernel/trace/trace_events_hist.c
View File

@ -419,6 +419,8 @@ struct action_data {
*/
unsigned int var_ref_idx;
struct synth_event *synth_event;
bool use_trace_keyword;
char *synth_event_name;
union {
struct {
@ -3700,6 +3702,8 @@ static void action_data_destroy(struct action_data *data)
if (data->synth_event)
data->synth_event->ref--;
kfree(data->synth_event_name);
kfree(data);
}
@ -3781,6 +3785,7 @@ static int track_data_create(struct hist_trigger_data *hist_data,
static int parse_action_params(char *params, struct action_data *data)
{
char *param, *saved_param;
bool first_param = true;
int ret = 0;
while (params) {
@ -3809,6 +3814,13 @@ static int parse_action_params(char *params, struct action_data *data)
goto out;
}
if (first_param && data->use_trace_keyword) {
data->synth_event_name = saved_param;
first_param = false;
continue;
}
first_param = false;
data->params[data->n_params++] = saved_param;
}
out:
@ -3886,6 +3898,9 @@ static int action_parse(char *str, struct action_data *data,
} else {
char *params = strsep(&str, ")");
if (str_has_prefix(action_name, "trace"))
data->use_trace_keyword = true;
if (params) {
ret = parse_action_params(params, data);
if (ret)
@ -4088,13 +4103,19 @@ static int trace_action_create(struct hist_trigger_data *hist_data,
unsigned int i, var_ref_idx;
unsigned int field_pos = 0;
struct synth_event *event;
char *synth_event_name;
int ret = 0;
lockdep_assert_held(&event_mutex);
event = find_synth_event(data->action_name);
if (data->use_trace_keyword)
synth_event_name = data->synth_event_name;
else
synth_event_name = data->action_name;
event = find_synth_event(synth_event_name);
if (!event) {
hist_err("trace action: Couldn't find synthetic event: ", data->action_name);
hist_err("trace action: Couldn't find synthetic event: ", synth_event_name);
return -EINVAL;
}
@ -4841,8 +4862,10 @@ static void print_action_spec(struct seq_file *m,
seq_puts(m, ",");
}
} else if (data->action == ACTION_TRACE) {
if (data->use_trace_keyword)
seq_printf(m, "%s", data->synth_event_name);
for (i = 0; i < data->n_params; i++) {
if (i)
if (i || data->use_trace_keyword)
seq_puts(m, ",");
seq_printf(m, "%s", data->params[i]);
}
@ -4890,6 +4913,7 @@ static bool actions_match(struct hist_trigger_data *hist_data,
for (i = 0; i < hist_data->n_actions; i++) {
struct action_data *data = hist_data->actions[i];
struct action_data *data_test = hist_data_test->actions[i];
char *action_name, *action_name_test;
if (data->handler != data_test->handler)
return false;
@ -4904,7 +4928,17 @@ static bool actions_match(struct hist_trigger_data *hist_data,
return false;
}
if (strcmp(data->action_name, data_test->action_name) != 0)
if (data->use_trace_keyword)
action_name = data->synth_event_name;
else
action_name = data->action_name;
if (data_test->use_trace_keyword)
action_name_test = data_test->synth_event_name;
else
action_name_test = data_test->action_name;
if (strcmp(action_name, action_name_test) != 0)
return false;
if (data->handler == HANDLER_ONMATCH) {