Re: [PATCH v7 05/16] tracing: Generalize hist trigger onmax and save action

Namhyung Kim
2018-11-23T07:01:10Z

On Wed, Nov 14, 2018 at 02:18:02PM -0600, Tom Zanussi wrote:
> From: Tom Zanussi <tom.zanussi@linux.intel.com>
>
> The action refactor code allowed actions and handlers to be separated,
> but the existing onmax handler and save action code is still not
> flexible enough to handle arbitrary coupling. This change generalizes
> them and in the process makes additional handlers and actions easier
> to implement.
>
> The onmax action can be broken up and thought of as two separate
> components - a variable to be tracked (the parameter given to the
> onmax($var_to_track) function) and an invisible variable created to
> save the ongoing result of doing something with that variable, such as
> saving the max value of that variable so far seen.
>
> Separating it out like this and renaming it appropriately allows us to
> use the same code for similar tracking functions such as
> onchange($var_to_track), which would just track the last value seen
> rather than the max seen so far, which is useful in some situations.
>
> Additionally, because different handlers and actions may want to save
> and access data differently e.g. save and retrieve tracking values as
> local variables vs something more global, save_val() and get_val()
> interface functions are introduced and max-specific implementations
> are used instead.
>
> The same goes for the code that checks whether a maximum has been hit
> - a generic check_val() interface and max-checking implementation is
> used instead, which allows future patches to make use of he same code
> using their own implemetations of similar functionality.
>
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
> kernel/trace/trace_events_hist.c | 225 ++++++++++++++++++++++++++-------------
> 1 file changed, 151 insertions(+), 74 deletions(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 54b78cfe2766..ac48ad1482c8 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -319,6 +319,15 @@ typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
> struct ring_buffer_event *rbe,
> struct action_data *data, u64 *var_ref_vals);
>
> +typedef bool (*check_track_val_fn_t) (u64 track_val, u64 var_val);
> +typedef bool (*save_track_val_fn_t) (struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data,
> + unsigned int track_var_idx, u64 var_val);
> +typedef u64 (*get_track_val_fn_t) (struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data);
> +
> enum handler_id {
> HANDLER_ONMATCH = 1,
> HANDLER_ONMAX,
> @@ -349,14 +358,18 @@ struct action_data {
>
> struct {
> char *var_str;
> - unsigned int max_var_ref_idx;
> - struct hist_field *max_var;
> - struct hist_field *var;
> - } onmax;
> + struct hist_field *var_ref;
> + unsigned int var_ref_idx;
> +
> + struct hist_field *track_var;
> +
> + check_track_val_fn_t check_val;
> + save_track_val_fn_t save_val;
> + get_track_val_fn_t get_val;
> + } track_data;
> };
> };
>
> -
> static char last_hist_cmd[MAX_FILTER_STR_VAL];
> static char hist_err_str[MAX_FILTER_STR_VAL];
>
> @@ -3133,10 +3146,10 @@ static void update_field_vars(struct hist_trigger_data *hist_data,
> hist_data->n_field_vars, 0);
> }
>
> -static void update_max_vars(struct hist_trigger_data *hist_data,
> - struct tracing_map_elt *elt,
> - struct ring_buffer_event *rbe,
> - void *rec)
> +static void update_save_vars(struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct ring_buffer_event *rbe,
> + void *rec)
> {
> __update_field_vars(elt, rbe, rec, hist_data->save_vars,
> hist_data->n_save_vars, hist_data->n_field_var_str);
> @@ -3274,14 +3287,68 @@ create_target_field_var(struct hist_trigger_data *target_hist_data,
> return create_field_var(target_hist_data, file, var_name);
> }
>
> -static void onmax_print(struct seq_file *m,
> - struct hist_trigger_data *hist_data,
> - struct tracing_map_elt *elt,
> - struct action_data *data)
> +static bool check_track_val_max(u64 track_val, u64 var_val)
> {
> - unsigned int i, save_var_idx, max_idx = data->onmax.max_var->var.idx;
> + if (var_val <= track_val)
> + return false;
> +
> + return true;
> +}
>
> - seq_printf(m, "\n\tmax: %10llu", tracing_map_read_var(elt, max_idx));
> +static u64 get_track_val_local(struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data)
> +{
> + unsigned int track_var_idx = data->track_data.track_var->var.idx;
> + u64 track_val;
> +
> + track_val = tracing_map_read_var(elt, track_var_idx);
> +
> + return track_val;
> +}
> +
> +static bool save_track_val_local(struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data,
> + unsigned int track_var_idx, u64 var_val)
> +{
> + bool ret = false;
> + u64 track_val;
> +
> + track_val = tracing_map_read_var(elt, track_var_idx);
> +
> + if (data->track_data.check_val(track_val, var_val)) {
> + tracing_map_set_var(elt, track_var_idx, var_val);
> + ret = true;
> + }
> +
> + return ret;
> +}
> +
> +static bool update_track_val(struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data, u64 *var_ref_vals)
> +{
> + unsigned int track_var_idx = data->track_data.track_var->var.idx;
> + unsigned int track_var_ref_idx = data->track_data.var_ref_idx;
> + u64 var_val;
> +
> + var_val = var_ref_vals[track_var_ref_idx];
> +
> + return data->track_data.save_val(hist_data, elt, data,
> + track_var_idx, var_val);
> +}

It's bit confusing for me update_track_val() calls ->save_val() and it
in turn calls ->check_val(). Why not having wrappers corresponding to
their callback name? - get_track_val(), check_track_val() and
save_trace_val()...

> +
> +static void track_data_print(struct seq_file *m,
> + struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt,
> + struct action_data *data)
> +{
> + u64 track_val = data->track_data.get_val(hist_data, elt, data);
> + unsigned int i, save_var_idx;
> +
> + if (data->handler == HANDLER_ONMAX)
> + seq_printf(m, "\n\tmax: %10llu", track_val);
>
> for (i = 0; i < hist_data->n_save_vars; i++) {
> struct hist_field *save_val = hist_data->save_vars[i]->val;
> @@ -3300,25 +3367,13 @@ static void onmax_print(struct seq_file *m,
> }
> }
>
> -static void onmax_save(struct hist_trigger_data *hist_data,
> - struct tracing_map_elt *elt, void *rec,
> - struct ring_buffer_event *rbe,
> - struct action_data *data, u64 *var_ref_vals)
> +static void ontrack_save(struct hist_trigger_data *hist_data,
> + struct tracing_map_elt *elt, void *rec,
> + struct ring_buffer_event *rbe,
> + struct action_data *data, u64 *var_ref_vals)
> {
> - unsigned int max_idx = data->onmax.max_var->var.idx;
> - unsigned int max_var_ref_idx = data->onmax.max_var_ref_idx;
> -
> - u64 var_val, max_val;
> -
> - var_val = var_ref_vals[max_var_ref_idx];
> - max_val = tracing_map_read_var(elt, max_idx);
> -
> - if (var_val <= max_val)
> - return;
> -
> - tracing_map_set_var(elt, max_idx, var_val);
> -
> - update_max_vars(hist_data, elt, rbe, rec);
> + if (update_track_val(hist_data, elt, data, var_ref_vals))
> + update_save_vars(hist_data, elt, rbe, rec);

... and then it should look like:

if (check_track_val()) {
save_track_val();
update_save_vars();
}

I also think update_save_vars() also needs to be renamed something
like save_track_vars() or save_trace_data().

Thanks,
Namhyung

> }