Messages in this thread | | | Date | Thu, 22 Jul 2021 22:29:24 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v2] tracing: Allow execnames to be passed as args for synthetic events |
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On Wed, 21 Jul 2021 21:47:02 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org> > > Allow common_pid.execname to be saved in a variable in one histogram to be > passed to another histogram that can pass it as a parameter to a synthetic > event. > > ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs:arg2=common_pid.execname' \ > > events/sched/sched_waking/trigger > ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > synthetic_events > ># echo 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs-$__arg__1,exec=$arg2'\ > ':onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,$exec)' \ > > events/sched/sched_switch/trigger > > The above is a wake up latency synthetic event setup that passes the execname > of the common_pid that woke the task to the scheduling of that task, which > triggers a synthetic event that passes the original execname as a > parameter to display it. > > ># echo 1 > events/synthetic/enable > ># cat trace > <idle>-0 [006] d..4 186.863801: wakeup_lat: pid=1306 delta=65 wake_comm=kworker/u16:3 > <idle>-0 [000] d..4 186.863858: wakeup_lat: pid=163 delta=27 wake_comm=<idle> > <idle>-0 [001] d..4 186.863903: wakeup_lat: pid=1307 delta=36 wake_comm=kworker/u16:4 > <idle>-0 [000] d..4 186.863927: wakeup_lat: pid=163 delta=5 wake_comm=<idle> > <idle>-0 [006] d..4 186.863957: wakeup_lat: pid=1306 delta=24 wake_comm=kworker/u16:3 > sshd-1306 [006] d..4 186.864051: wakeup_lat: pid=61 delta=62 wake_comm=<idle> > <idle>-0 [000] d..4 186.965030: wakeup_lat: pid=609 delta=18 wake_comm=<idle> > <idle>-0 [006] d..4 186.987582: wakeup_lat: pid=1306 delta=65 wake_comm=kworker/u16:3 > <idle>-0 [000] d..4 186.987639: wakeup_lat: pid=163 delta=27 wake_comm=<idle> >
This looks an interesting improvement. If we can do this, can we also filter the event by 'comm' (or execname)?
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > Changes since v1: > - Hit a bug on freeing the histogram, found that I used "char[]" for the > type, and it expects to be freed. Freed the old "type" and still use > "char[]" but have the normal freeing use kfree_const() on type.
BTW, if we can use this technic on the hist_field->type, we can cleanup other type = strdup("<any const type>", GFP_KERNEL) with type = "<any const type>" ?
Anyway, that will be done in another patch (I think that should be done first, then we can avoid an odd kfree() in update_var_execname().)
Thank you,
> > kernel/trace/trace_events_hist.c | 49 ++++++++++++++++++++++++++++---- > 1 file changed, 44 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 34325f41ebc0..bb1956efd5ef 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -1395,17 +1395,17 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) > struct hist_trigger_data *hist_data = elt->map->private_data; > unsigned int size = TASK_COMM_LEN; > struct hist_elt_data *elt_data; > - struct hist_field *key_field; > + struct hist_field *hist_field; > unsigned int i, n_str; > > elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL); > if (!elt_data) > return -ENOMEM; > > - for_each_hist_key_field(i, hist_data) { > - key_field = hist_data->fields[i]; > + for_each_hist_field(i, hist_data) { > + hist_field = hist_data->fields[i]; > > - if (key_field->flags & HIST_FIELD_FL_EXECNAME) { > + if (hist_field->flags & HIST_FIELD_FL_EXECNAME) { > elt_data->comm = kzalloc(size, GFP_KERNEL); > if (!elt_data->comm) { > kfree(elt_data); > @@ -1589,7 +1589,9 @@ static void __destroy_hist_field(struct hist_field *hist_field) > > kfree(hist_field->var.name); > kfree(hist_field->name); > - kfree(hist_field->type); > + > + /* execname vars use a constant type */ > + kfree_const(hist_field->type); > > kfree(hist_field->system); > kfree(hist_field->event_name); > @@ -3707,6 +3709,40 @@ static int create_val_field(struct hist_trigger_data *hist_data, > return __create_val_field(hist_data, val_idx, file, NULL, field_str, 0); > } > > +static const char *no_comm = "(no comm)"; > + > +static u64 hist_field_execname(struct hist_field *hist_field, > + struct tracing_map_elt *elt, > + struct trace_buffer *buffer, > + struct ring_buffer_event *rbe, > + void *event) > +{ > + struct hist_elt_data *elt_data; > + > + if (WARN_ON_ONCE(!elt)) > + return (u64)(unsigned long)no_comm; > + > + elt_data = elt->private_data; > + > + if (WARN_ON_ONCE(!elt_data->comm)) > + return (u64)(unsigned long)no_comm; > + > + return (u64)(unsigned long)(elt_data->comm); > +} > + > +/* Convert a var that points to common_pid.execname to a string */ > +static void update_var_execname(struct hist_field *hist_field) > +{ > + hist_field->flags = HIST_FIELD_FL_STRING | HIST_FIELD_FL_VAR | > + HIST_FIELD_FL_EXECNAME; > + hist_field->size = MAX_FILTER_STR_VAL; > + hist_field->is_signed = 0; > + kfree(hist_field->type); > + /* This uses kfree_const() to free */ > + hist_field->type = "char[]"; > + hist_field->fn = hist_field_execname; > +} > + > static int create_var_field(struct hist_trigger_data *hist_data, > unsigned int val_idx, > struct trace_event_file *file, > @@ -3731,6 +3767,9 @@ static int create_var_field(struct hist_trigger_data *hist_data, > > ret = __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags); > > + if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME) > + update_var_execname(hist_data->fields[val_idx]); > + > if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_STRING) > hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++; > > -- > 2.31.1 >
-- Masami Hiramatsu <mhiramat@kernel.org>
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