Hi Tom,
On Wed, Dec 06, 2017 at 04:38:03PM -0600, Tom Zanussi wrote:
> Add the necessary infrastructure to allow the variables defined on one
> event to be referenced in another. This allows variables set by a
> previous event to be referenced and used in expressions combining the
> variable values saved by that previous event and the event fields of
> the current event. For example, here's how a latency can be
> calculated and saved into yet another variable named 'wakeup_lat':
>
> # echo 'hist:keys=pid,prio:ts0=common_timestamp ...
> # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...
>
> In the first event, the event's timetamp is saved into the variable
> ts0. In the next line, ts0 is subtracted from the second event's
> timestamp to produce the latency.
>
> Further users of variable references will be described in subsequent
> patches, such as for instance how the 'wakeup_lat' variable above can
> be displayed in a latency histogram.
>
> Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
> ---
[SNIP]
> @@ -313,10 +529,150 @@ static struct hist_field *find_var(struct
> hist_trigger_data *hist_data,
> return NULL;
> }
>
> +static struct trace_event_file *find_var_file(struct trace_array *tr,
> + char *system,
> + char *event_name,
> + char *var_name)
> +{
> + struct hist_trigger_data *var_hist_data;
> + struct hist_var_data *var_data;
> + struct trace_event_call *call;
> + struct trace_event_file *file, *found = NULL;
> + const char *name;
> +
> + list_for_each_entry(var_data, &tr->hist_vars, list) {
> + var_hist_data = var_data->hist_data;
> + file = var_hist_data->event_file;
> + if (file == found)
> + continue;
> + call = file->event_call;
> + name = trace_event_name(call);
> +
> + if (!system || !event_name) {
> + if (find_var(var_hist_data, file, var_name)) {
Is find_var() really needed? I guess find_var_field() could do the
job with lower overhead..
> + if (found) {
> + return NULL;
> + }
> +
> + found = file;
> + }
> + continue;
> + }
> +
> + if (strcmp(event_name, name) != 0)
> + continue;
> + if (strcmp(system, call->class->system) != 0)
> + continue;
Also it doesn't need to iterate the loop when system and event name is
given. Please see below
> +
> + found = file;
> + break;
> + }
> +
> + return found;
> +}
How about this?
find_var_file()
{
if (system)
return find_event_file(tr, system, event);
list_for_each_entry(var_data, &tr->hist_vars, list) {
var_hist_data = var_data->hist_data;
file = var_hist_data->event_file;
if (file == found)
continue;
if (find_var_field(var_hist_data, var_name)) {
if (found)
return NULL;
found = file;
}
}
}
Thanks,
Namhyung
