Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 2 Dec 2022 10:08:04 -0800 | Subject | Re: [PATCH v2 3/4] perf build: Use libtraceevent from the system |
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On Wed, Nov 30, 2022 at 12:13 PM Ian Rogers <irogers@google.com> wrote: > > On Wed, Nov 30, 2022 at 11:05 AM Namhyung Kim <namhyung@kernel.org> wrote: > > > > On Tue, Nov 29, 2022 at 10:30 PM Ian Rogers <irogers@google.com> wrote: > > > > > > Remove the LIBTRACEEVENT_DYNAMIC and LIBTRACEFS_DYNAMIC. If > > > libtraceevent isn't installed or NO_LIBTRACEEVENT=1 is passed to the > > > build, don't compile in libtraceevent and libtracefs support. This > > > also disables CONFIG_TRACE that controls "perf > > > trace". CONFIG_TRACEEVENT is used to control enablement in > > > Build/Makefiles, HAVE_LIBTRACEEVENT is used in C code. Without > > > HAVE_LIBTRACEEVENT tracepoints are disabled and as such the commands > > > kmem, kwork, lock, sched and timechart are removed. The majority of > > > commands continue to work including "perf test". > > > > Maybe we can have a different approach. I guess the trace data > > access is isolated then we can make dummy interfaces when there's > > no libtraceevent. This way we don't need to touch every command > > and let it fail when it's asked. > > Sounds like a worthwhile refactor that can land on top of this change. > > > The motivation is that we should be able to run the sub-commands > > as much as possible. In fact, we could run 'record' part only on the > > target machine and pass the data to the host for analysis with a > > full-fledged perf. Also some commands like 'perf lock contention' > > can run with or without libtraceevent (using BPF only). > > The issue here is that perf lock contention will use evsel__new_tp and > internally that uses libtraceevent. As such it is removed without > HAVE_LIBTRACEEVENT. Without the evsel there's not much perf lock > contention can do, so rather than litter the code with > HAVE_LIBTRACEEVENT and for it to be broken, I made the choice just to > remove it from the no libtraceevent build for now.
I don't think it needs evsel__new_tp() when BPF is used. The BPF program is attached to the raw tracepoint without perf_event and the result is written to the BPF map.
> > I think it is worth pursuing these patches in the shape they are in so > that we can land the removal of tools/lib/traceevent and ensure the > migration away from an out-of-date version of that library.
Yeah, I agree that we should remove the stale libtraceevent but I'd like to do it with minimal changes in the perf code base. Let me take a look at this.
Thanks, Namhyung
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