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| author | Tom Zanussi <zanussi@kernel.org> | 2020-10-05 00:14:06 +0200 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-10-06 01:32:18 +0200 |
| commit | bd82631d7ccdc894af2738e47abcba2cb6e7dea9 (patch) | |
| tree | 126830cac997b235cc18f4cb7b6e09236ca0bbb0 /kernel/trace/trace_events_hist.c | |
| parent | tracing: Save normal string variables (diff) | |
| download | linux-bd82631d7ccdc894af2738e47abcba2cb6e7dea9.tar.xz linux-bd82631d7ccdc894af2738e47abcba2cb6e7dea9.zip | |
tracing: Add support for dynamic strings to synthetic events
Currently, sythetic events only support static string fields such as:
# echo 'test_latency u64 lat; char somename[32]' > /sys/kernel/debug/tracing/synthetic_events
Which is fine, but wastes a lot of space in the event.
It also prevents the most commonly-defined strings in the existing
trace events e.g. those defined using __string(), from being passed to
synthetic events via the trace() action.
With this change, synthetic events with dynamic fields can be defined:
# echo 'test_latency u64 lat; char somename[]' > /sys/kernel/debug/tracing/synthetic_events
And the trace() action can be used to generate events using either
dynamic or static strings:
# echo 'hist:keys=name:lat=common_timestamp.usecs-$ts0:onmatch(sys.event).test_latency($lat,name)' > /sys/kernel/debug/tracing/events
The synthetic event dynamic strings are implemented in the same way as
the existing __data_loc strings and appear as such in the format file.
[ <rostedt@goodmis.org>: added __set_synth_event_print_fmt() changes:
I added the following to make it work with trace-cmd. Dynamic strings
must have __get_str() for events in the print_fmt otherwise it can't be
parsed correctly. ]
Link: https://lore.kernel.org/r/cover.1601588066.git.zanussi@kernel.org
Link: https://lkml.kernel.org/r/3ed35b6d0e390f5b94cb4a9ba1cc18f5982ab277.1601848695.git.zanussi@kernel.org
Tested-by: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_events_hist.c')
| -rw-r--r-- | kernel/trace/trace_events_hist.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 812bc5f94b5c..c74a7d157306 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -3289,6 +3289,15 @@ static int check_synth_field(struct synth_event *event, field = event->fields[field_pos]; + /* + * A dynamic string synth field can accept static or + * dynamic. A static string synth field can only accept a + * same-sized static string, which is checked for later. + */ + if (strstr(hist_field->type, "char[") && field->is_string + && field->is_dynamic) + return 0; + if (strcmp(field->type, hist_field->type) != 0) { if (field->size != hist_field->size || field->is_signed != hist_field->is_signed) |