Messages in this thread | | | Subject | Re: [PATCH v2 2/2] tracing: Allow execnames to be passed as args for synthetic events | From | Tom Zanussi <> | Date | Thu, 22 Jul 2021 17:09:48 -0500 |
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Hi Steve,
On Thu, 2021-07-22 at 10:27 -0400, Steven Rostedt 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.execna > me' \ > > 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> > > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > kernel/trace/trace_events_hist.c | 46 +++++++++++++++++++++++++++++- > -- > 1 file changed, 42 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c > b/kernel/trace/trace_events_hist.c > index 5c9082201bc2..14b840de1326 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); > @@ -3703,6 +3703,41 @@ 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_const(hist_field->type); > + 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, > @@ -3727,6 +3762,9 @@ 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++; >
Yeah, the common_pid.execname thing is kind of a strange beast, and I think this is actually a nice and reasonable way to deal with it for this case.
Thanks,
Reviewed-by: <zanussi@kernel.org>
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