From: Steven Rostedt <rostedt@goodmis.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] tracing: Allow execnames to be passed as args for synthetic events
Date: Wed, 21 Jul 2021 20:15:48 -0400 [thread overview]
Message-ID: <20210721201548.5f4262a3@oasis.local.home> (raw)
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>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_events_hist.c | 43 +++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 34325f41ebc0..6060eb009647 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);
@@ -3707,6 +3707,38 @@ 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;
+ 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 +3763,9 @@ 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
reply other threads:[~2021-07-22 0:15 UTC|newest]
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