Messages in this thread | | | From | Masami Hiramatsu <> | Subject | [PATCH 0/5] tracing: Add __rel_loc support | Date | Mon, 15 Nov 2021 19:19:59 +0900 |
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Hello Beau,
(Sorry, if you get the same copy. I resend this because I made a typo on the mail address.)
Here is a series of patches to add support of '__rel_loc' relative dynamic array attribute support. Note that this is only for the kernel side code, user space tools might need to be updated for decoding '__rel_loc' too. There are 2 patches for libtraceevent and perftools, but not those are not tested yet. I added it for review.
Here are 3 patches, [1/5] is the main and required patch, which updates the event filter, histogram, and inject for __rel_loc.
[2/5] and [3/5] are for testing. I think those are no needed to be merged. I just made it for the testing. [4/5] is updating libtraceevent, which allows libtraceevent user to decode the __rel_loc via libtraceevent API. Since perf-tools decodes the event by itself, it needs [5/5]. (Note that I haven't tested fully yet)
Steve, please tell me if I missed some parts or features which need to decode the dynamic string or data.
The __rel_loc -----
The '__data_loc' is used for encoding the dynamic data location on the trace event record. But '__data_loc' is not useful if the writer doesn't know the event header (e.g. user event), because it records the dynamic data offset from the entry of the record, not the field itself.
This new '__rel_loc' attribute encodes the data location relatively from the next of the field. For example, when there is a record like below (the number in the parentheses is the size of fields)
|header(N)|common(M)|fields(K)|__data_loc(4)|fields(L)|data(G)|
In this case, '__data_loc' field will be
__data_loc = (G << 16) | (N+M+K+4+L)
If '__rel_loc' is used, this will be
|header(N)|common(M)|fields(K)|__rel_loc(4)|fields(L)|data(G)|
where
__rel_loc = (G << 16) | (L)
(Because there is L bytes after the '__rel_loc' attribute field)
This is relatively easy (and no need to consider the kernel header change) when the event data fields are composed by user who doesn't know header and common fields.
Test Event Injection ---- / # modprobe trace-events-sample.ko / # cd /sys/kernel/tracing/ /sys/kernel/tracing # echo 'foo="test" bar=0' >> events/sample-trace/foo_rel_loc /inject /sys/kernel/tracing # cat trace # tracer: nop # # entries-in-buffer/entries-written: 1/1 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <...>-135 [002] ..... 153.998779: foo_rel_loc: foo_rel_loc test, 0
Test Event Histogram ----
/sys/kernel/tracing # echo 'hist:key=foo' >> events/sample-trace/foo_rel_loc/trigger /sys/kernel/tracing # cat events/sample-trace/foo_rel_loc/hist # event histogram # # trigger info: hist:keys=foo:vals=hitcount:sort=hitcount:size=2048 [active] #
{ foo: Hello __rel_loc } hitcount: 11
Totals: Hits: 11 Entries: 1 Dropped: 0
Test Event Filter ---- /sys/kernel/tracing # echo 'foo == "Hello __rel_loc"' >> events/sample-trace/foo_rel_loc/filter /sys/kernel/tracing # echo > trace /sys/kernel/tracing # echo 1 > events/sample-trace/foo_rel_loc/enable /sys/kernel/tracing # cat trace # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | event-sample-142 [005] ..... 665.801471: foo_rel_loc: foo_rel_loc Hello __rel_loc, 631 event-sample-142 [005] ..... 666.825611: foo_rel_loc: foo_rel_loc Hello __rel_loc, 632
Thank you,
---
Masami Hiramatsu (5): tracing: Support __rel_loc relative dynamic data location attribute tracing: Add '__rel_loc' using trace event macros samples/trace_event: Add '__rel_loc' using sample event libtraceevent: Add __rel_loc relative location attribute support tools/perf: Add __rel_loc support
include/linux/trace_events.h | 1 include/trace/bpf_probe.h | 13 +++ include/trace/perf.h | 13 +++ include/trace/trace_events.h | 83 ++++++++++++++++++++ kernel/trace/trace.h | 4 + kernel/trace/trace_events_filter.c | 32 +++++++- kernel/trace/trace_events_hist.c | 21 +++++ kernel/trace/trace_events_inject.c | 11 ++- samples/trace_events/trace-events-sample.c | 2 samples/trace_events/trace-events-sample.h | 28 +++++++ tools/lib/traceevent/event-parse.c | 14 +++ tools/lib/traceevent/event-parse.h | 1 tools/lib/traceevent/parse-filter.c | 5 + tools/perf/builtin-trace.c | 2 tools/perf/util/data-convert-bt.c | 2 tools/perf/util/evsel.c | 2 tools/perf/util/python.c | 2 .../perf/util/scripting-engines/trace-event-perl.c | 2 .../util/scripting-engines/trace-event-python.c | 2 tools/perf/util/sort.c | 2 20 files changed, 235 insertions(+), 7 deletions(-)
-- Masami Hiramatsu (Linaro) <mhiramat@kernel.org>
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