| Message ID | 20220531172435.2a51eff3@rorschach.local.home (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | deb54b1d20f6bae4fff7ce195540b81fedfb2bd0 |
| Headers | show |
| Series | libtracefs: Allow for the same event to be start and end in tracefs_sql() | expand |
On Tue, 2022-05-31 at 17:24 -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > When creating a synthetic event that is based off of the same event with > two different fields, it should still work. But the assumption was that > every field that has a label will have the same label, which is not > true. > > For example, to create an event that measures the time a task is > blocked, it needs to start and end on the same event (sched_switch), but > just use different fields. > > sqlhist -n blocked 'SELECT end.next_pid AS pid,end.next_comm AS comm,(end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) AS lat > FROM sched_switch AS start JOIN sched_switch AS end ON start.prev_pid = end.next_pid WHERE start.prev_state = 2' > > But this gave the following error: > > Failed creating synthetic event!: Success > SELECT end.next_pid AS pid,end.next_comm AS comm,(end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) AS lat FROM sched_switch AS start JOIN sched_switch AS end ON start.prev_pid = end.next_pid WHERE > start.prev_state = 2 > ^ > ERROR: 'end.next_pid' > 'start.prev_pid' and 'end.next_pid' must be a field for each event: 'sched_switch' and 'sched_switch' > > Because the end sched_switch would already have the label "start" and it > would not create one for "end" making the "end" not resolve correctly. > > Now it gives the correct answer: > > echo 's:blocked pid_t next_pid; char next_comm[16]; u64 lat;' >> /sys/kernel/tracing/dynamic_events > echo 'hist:keys=prev_pid:__arg_21065_1=next_pid,__arg_21065_2=next_comm,__arg_21065_3=common_timestamp.usecs if prev_state == 2' >> /sys/kernel/tracing/events/sched/sched_switch/trigger > echo 'hist:keys=next_pid:next_pid=$__arg_21065_1,next_comm=$__arg_21065_2,lat=common_timestamp.usecs-$__arg_21065_3:onmatch(sched.sched_switch).trace(blocked,$next_pid,$next_comm,$lat)' >> > /sys/kernel/tracing/events/sched/sched_switch/trigger > > Fixes: 25446407 ("libtracefs: Added new API tracefs_sql()") > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Tested-by: Harald Seiler <hws@denx.de> Just gave it a spin, this is great! > --- > src/tracefs-sqlhist.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/src/tracefs-sqlhist.c b/src/tracefs-sqlhist.c > index 9811362..cee037b 100644 > --- a/src/tracefs-sqlhist.c > +++ b/src/tracefs-sqlhist.c > @@ -285,6 +285,8 @@ static struct expr *find_field(struct sqlhist_bison *sb, > if (!strcmp(field->raw, raw)) { > if (label && !field->label) > field->label = label; > + if (label && strcmp(label, field->label) != 0) > + continue; > return expr; > } >
diff --git a/src/tracefs-sqlhist.c b/src/tracefs-sqlhist.c index 9811362..cee037b 100644 --- a/src/tracefs-sqlhist.c +++ b/src/tracefs-sqlhist.c @@ -285,6 +285,8 @@ static struct expr *find_field(struct sqlhist_bison *sb, if (!strcmp(field->raw, raw)) { if (label && !field->label) field->label = label; + if (label && strcmp(label, field->label) != 0) + continue; return expr; }