[PATCH v5 7/8] tracing: Add hist trigger onchange() handler
From: Tom Zanussi
Date: Mon Oct 01 2018 - 12:19:04 EST
From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Add support for a hist:onchange($var) handler, similar to the onmax()
handler but triggering whenever there's any change in $var, not just a
max.
Also, add a testcase for it.
Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
Documentation/trace/histogram.rst | 97 ++++++++++++++++++++++
kernel/trace/trace_events_hist.c | 68 ++++++++++++---
.../inter-event/trigger-onchange-action-hist.tc | 43 ++++++++++
3 files changed, 195 insertions(+), 13 deletions(-)
create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-onchange-action-hist.tc
diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst
index ce715dc0ec2c..e73a840a3598 100644
--- a/Documentation/trace/histogram.rst
+++ b/Documentation/trace/histogram.rst
@@ -2109,6 +2109,103 @@ hist trigger specification.
<...>-2102 [005] d..4 309.875185: sched_wake_idle_without_ipi: cpu=1
<idle>-0 [001] d..3 309.875200: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=S ==> next_comm=cyclictest next_pid=2103 next_prio=19
+ - onchange(var).save(field,.. .)
+
+ The 'onchange(var).save(field,...)' hist trigger action is invoked
+ whenever the value of 'var' associated with a histogram entry
+ changes.
+
+ The end result is that the trace event fields specified as the
+ onchange.save() params will be saved if 'var' changes for that
+ hist trigger entry. This allows context from the event that
+ changed the value to be saved for later reference. When the
+ histogram is displayed, additional fields displaying the saved
+ values will be printed.
+
+ - onchange(var).snapshot()
+
+ The 'onchange(var).snapshot()' hist trigger action is invoked
+ whenever the value of 'var' associated with a histogram entry
+ changes.
+
+ The end result is that a global snapshot of the trace buffer will
+ be saved in the tracing/snapshot file if 'var' changes for any
+ hist trigger entry.
+
+ Note that in this case the changed value is a global variable
+ associated withe current trace instance. The key of the specific
+ trace event that caused the value to change and the global value
+ itself are displayed, along with a message stating that a snapshot
+ has been taken and where to find it. The user can use the key
+ information displayed to locate the corresponding bucket in the
+ histogram for even more detail.
+
+ As an example the below defines a hist trigger on the tcp_probe
+ event, keyed on dport. Whenever a tcp_probe event occurs, the
+ cwnd field is checked against the current value stored in the
+ $cwnd variable. If the value has changed, a snapshot is taken.
+ As part of the setup, all the scheduler and tcp events are also
+ enabled, which are the events that will show up in the snapshot
+ when it is taken at some point:
+
+ # echo 1 > /sys/kernel/debug/tracing/events/sched/enable
+ # echo 1 > /sys/kernel/debug/tracing/events/tcp/enable
+
+ # echo 'hist:keys=dport:cwnd=snd_cwnd: \
+ onchange($cwnd).save(snd_wnd,srtt,rcv_wnd): \
+ onchange($cwnd).snapshot()' >> \
+ /sys/kernel/debug/tracing/events/tcp/tcp_probe/trigger
+
+ When the histogram is displayed, for each bucket the tracked value
+ and the saved values corresponding to that value are displayed
+ following the rest of the fields.
+
+ If a snaphot was taken, there is also a message indicating that,
+ along with the value and event that triggered the snapshot:
+
+ # cat /sys/kernel/debug/tracing/events/tcp/tcp_probe/hist
+ { dport: 1521 } hitcount: 8
+ changed: 10 snd_wnd: 35456 srtt: 154262 rcv_wnd: 42112
+
+ { dport: 80 } hitcount: 23
+ changed: 10 snd_wnd: 28960 srtt: 19604 rcv_wnd: 29312
+
+ { dport: 9001 } hitcount: 172
+ changed: 10 snd_wnd: 48384 srtt: 260444 rcv_wnd: 55168
+
+ { dport: 443 } hitcount: 211
+ changed: 10 snd_wnd: 26960 srtt: 17379 rcv_wnd: 28800
+
+ Snapshot taken (see tracing/snapshot). Details:
+ triggering value { onchange($cwnd) }: 10
+ triggered by event with key: { dport: 80 }
+
+ Totals:
+ Hits: 414
+ Entries: 4
+ Dropped: 0
+
+ In the above case, the event that triggered the snapshot has the
+ key with dport == 80. If you look at the bucket that has 80 as
+ the key, you'll find the additional values save()'d along with the
+ changed value for that bucket, which should be the same as the
+ global changed value (since that was the same value that triggered
+ the global snapshot).
+
+ And finally, looking at the snapshot data should show at or near
+ the end the event that triggered the snapshot:
+
+ # cat /sys/kernel/debug/tracing/snapshot
+
+ gnome-shell-1261 [006] dN.3 49.823113: sched_stat_runtime: comm=gnome-shell pid=1261 runtime=49347 [ns] vruntime=1835730389 [ns]
+ kworker/u16:4-773 [003] d..3 49.823114: sched_switch: prev_comm=kworker/u16:4 prev_pid=773 prev_prio=120 prev_state=R+ ==> next_comm=kworker/3:2 next_pid=135 next_prio=120
+ gnome-shell-1261 [006] d..3 49.823114: sched_switch: prev_comm=gnome-shell prev_pid=1261 prev_prio=120 prev_state=R+ ==> next_comm=kworker/6:2 next_pid=387 next_prio=120
+ kworker/3:2-135 [003] d..3 49.823118: sched_stat_runtime: comm=kworker/3:2 pid=135 runtime=5339 [ns] vruntime=17815800388 [ns]
+ kworker/6:2-387 [006] d..3 49.823120: sched_stat_runtime: comm=kworker/6:2 pid=387 runtime=9594 [ns] vruntime=14589605367 [ns]
+ kworker/6:2-387 [006] d..3 49.823122: sched_switch: prev_comm=kworker/6:2 prev_pid=387 prev_prio=120 prev_state=R+ ==> next_comm=gnome-shell next_pid=1261 next_prio=120
+ kworker/3:2-135 [003] d..3 49.823123: sched_switch: prev_comm=kworker/3:2 prev_pid=135 prev_prio=120 prev_state=T ==> next_comm=swapper/3 next_pid=0 next_prio=120
+ <idle>-0 [004] ..s7 49.823798: tcp_probe: src=10.0.0.10:54326 dest=23.215.104.193:80 mark=0x0 length=32 snd_nxt=0xe3ae2ff5 snd_una=0xe3ae2ecd snd_cwnd=10 ssthresh=2147483647 snd_wnd=28960 srtt=19604 rcv_wnd=29312
+
3. User space creating a trigger
--------------------------------
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 8d6e9fde0826..90f1a0cf34c0 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -331,6 +331,7 @@ typedef u64 (*get_track_val_fn_t) (struct hist_trigger_data *hist_data,
enum handler_id {
HANDLER_ONMATCH = 1,
HANDLER_ONMAX,
+ HANDLER_ONCHANGE,
};
enum action_id {
@@ -1886,7 +1887,8 @@ static int parse_action(char *str, struct hist_trigger_attrs *attrs)
return ret;
if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0) ||
- (strncmp(str, "onmax(", strlen("onmax(")) == 0)) {
+ (strncmp(str, "onmax(", strlen("onmax(")) == 0) ||
+ (strncmp(str, "onchange(", strlen("onchange(")) == 0)) {
attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
if (!attrs->action_str[attrs->n_actions]) {
ret = -ENOMEM;
@@ -3346,6 +3348,14 @@ static bool check_track_val_max(u64 track_val, u64 var_val)
return true;
}
+static bool check_track_val_changed(u64 track_val, u64 var_val)
+{
+ if (var_val == track_val)
+ return false;
+
+ return true;
+}
+
static u64 get_track_val_local(struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt,
struct action_data *data)
@@ -3520,6 +3530,8 @@ static void track_data_print(struct seq_file *m,
if (data->handler == HANDLER_ONMAX)
seq_printf(m, "\n\tmax: %10llu", track_val);
+ else if (data->handler == HANDLER_ONCHANGE)
+ seq_printf(m, "\n\tchanged: %10llu", track_val);
if (data->action == ACTION_SNAPSHOT)
return;
@@ -3550,10 +3562,10 @@ static void ontrack_save(struct hist_trigger_data *hist_data,
update_save_vars(hist_data, elt, rbe, rec);
}
-static void onmax_snapshot(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_snapshot(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)
{
update_track_val(hist_data, elt, data, var_ref_vals);
}
@@ -3614,14 +3626,14 @@ static int track_data_create(struct hist_trigger_data *hist_data,
track_data_var_str = data->track_data.var_str;
if (track_data_var_str[0] != '$') {
- hist_err("For onmax(x), x must be a variable: ", track_data_var_str);
+ hist_err("For onmax(x) or onchange(x), x must be a variable: ", track_data_var_str);
return -EINVAL;
}
track_data_var_str++;
var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
if (!var_field) {
- hist_err("Couldn't find onmax variable: ", track_data_var_str);
+ hist_err("Couldn't find onmax or onchange variable: ", track_data_var_str);
return -EINVAL;
}
@@ -3648,6 +3660,14 @@ static int track_data_create(struct hist_trigger_data *hist_data,
ret = PTR_ERR(track_var);
goto out;
}
+
+ if (data->handler == HANDLER_ONCHANGE)
+ track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
+ if (IS_ERR(track_var)) {
+ hist_err("Couldn't create onchange variable: ", "__change");
+ ret = PTR_ERR(track_var);
+ goto out;
+ }
data->track_data.track_var = track_var;
ret = action_create(hist_data, data);
@@ -3727,6 +3747,8 @@ static int action_parse(char *str, struct action_data *data,
if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;
else {
hist_err("action parsing: Handler doesn't support action: ", action_name);
ret = -EINVAL;
@@ -3750,6 +3772,8 @@ static int action_parse(char *str, struct action_data *data,
if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;
else {
hist_err("action parsing: Handler doesn't support action: ", action_name);
ret = -EINVAL;
@@ -3759,7 +3783,7 @@ static int action_parse(char *str, struct action_data *data,
data->track_data.save_val = save_track_val_snapshot;
data->track_data.get_val = get_track_val_snapshot;
- data->fn = onmax_snapshot;
+ data->fn = ontrack_snapshot;
data->action = ACTION_SNAPSHOT;
} else {
@@ -3773,6 +3797,8 @@ static int action_parse(char *str, struct action_data *data,
if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;
data->track_data.save_val = save_track_val_local;
data->track_data.get_val = get_track_val_local;
@@ -4638,7 +4664,8 @@ static void destroy_actions(struct hist_trigger_data *hist_data)
if (data->handler == HANDLER_ONMATCH)
onmatch_destroy(data);
- else if (data->handler == HANDLER_ONMAX)
+ else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
track_data_destroy(hist_data, data);
else
kfree(data);
@@ -4673,6 +4700,15 @@ static int parse_actions(struct hist_trigger_data *hist_data)
ret = PTR_ERR(data);
break;
}
+ } else if (strncmp(str, "onchange(", strlen("onchange(")) == 0) {
+ char *action_str = str + strlen("onchange(");
+
+ data = track_data_parse(hist_data, action_str,
+ HANDLER_ONCHANGE);
+ if (IS_ERR(data)) {
+ ret = PTR_ERR(data);
+ break;
+ }
} else {
ret = -EINVAL;
break;
@@ -4697,7 +4733,8 @@ static int create_actions(struct hist_trigger_data *hist_data)
ret = onmatch_create(hist_data, data);
if (ret)
return ret;
- } else if (data->handler == HANDLER_ONMAX) {
+ } else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE) {
ret = track_data_create(hist_data, data);
if (ret)
return ret;
@@ -4725,7 +4762,8 @@ static void print_actions(struct seq_file *m,
continue;
}
- if (data->handler == HANDLER_ONMAX)
+ if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
track_data_print(m, hist_data, elt, data);
}
}
@@ -4757,6 +4795,8 @@ static void print_track_data_spec(struct seq_file *m,
{
if (data->handler == HANDLER_ONMAX)
seq_puts(m, ":onmax(");
+ else if (data->handler == HANDLER_ONCHANGE)
+ seq_puts(m, ":onchange(");
seq_printf(m, "%s", data->track_data.var_str);
seq_printf(m, ").%s(", data->action_name);
@@ -4814,7 +4854,8 @@ static bool actions_match(struct hist_trigger_data *hist_data,
if (strcmp(data->match_data.event,
data_test->match_data.event) != 0)
return false;
- } else if (data->handler == HANDLER_ONMAX) {
+ } else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE) {
if (strcmp(data->track_data.var_str,
data_test->track_data.var_str) != 0)
return false;
@@ -4835,7 +4876,8 @@ static void print_actions_spec(struct seq_file *m,
if (data->handler == HANDLER_ONMATCH)
print_onmatch_spec(m, hist_data, data);
- else if (data->handler == HANDLER_ONMAX)
+ else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
print_track_data_spec(m, hist_data, data);
}
}
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-onchange-action-hist.tc b/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-onchange-action-hist.tc
new file mode 100644
index 000000000000..585f77f064f2
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/inter-event/trigger-onchange-action-hist.tc
@@ -0,0 +1,43 @@
+#!/bin/sh
+# description: event trigger - test inter-event histogram trigger onchange action
+
+do_reset() {
+ reset_trigger
+ echo > set_event
+ clear_trace
+}
+
+fail() { #msg
+ do_reset
+ echo $1
+ exit_fail
+}
+
+if [ ! -f set_event ]; then
+ echo "event tracing is not supported"
+ exit_unsupported
+fi
+
+if [ ! -f synthetic_events ]; then
+ echo "synthetic event is not supported"
+ exit_unsupported
+fi
+
+clear_synthetic_events
+reset_tracer
+do_reset
+
+echo "Test onchange action"
+
+echo 'hist:keys=comm:newprio=prio:onchange($newprio).save(comm,prio) if comm=="ping"' >> /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
+
+ping localhost -c 3
+nice -n 1 ping localhost -c 3
+
+if ! grep -q "changed:" events/sched/sched_waking/hist; then
+ fail "Failed to create onchange action inter-event histogram"
+fi
+
+do_reset
+
+exit 0
--
2.14.1