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tracing: Allow execnames to be passed as args for synthetic events 

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>

Link: https://lkml.kernel.org/r/20210722142837.458596338@goodmis.org

Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-07-22 10:27:07 -04:00
parent 3347d80baa
commit ed2cf90735
1 changed files with 42 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
kernel/trace/trace_events_hist.c
View File

@ -1420,17 +1420,17 @@ 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);
@ -3771,6 +3771,41 @@ 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,
@ -3795,6 +3830,9 @@ 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++;