Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 2 Dec 2022 15:36:24 -0800 | Subject | Re: [PATCH v2 3/4] perf build: Use libtraceevent from the system |
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On Fri, Dec 2, 2022 at 11:45 AM Ian Rogers <irogers@google.com> wrote: > > On Fri, Dec 2, 2022 at 10:29 AM Arnaldo Carvalho de Melo > <acme@kernel.org> wrote: > > > > Em Fri, Dec 02, 2022 at 10:08:04AM -0800, Namhyung Kim escreveu: > > > 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. > > > > Ok, was going to take a look at this patchkit, will wait for you now. > > > > - Arnaldo > > So the problematic function is: > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/evsel.c?h=perf/core#n482 > struct evsel *evsel__newtp_idx(const char *sys, const char *name, int idx) > > on success it will always initialize: > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/evsel.c?h=perf/core#n499 > evsel->tp_format = trace_event__tp_format(sys, name); > > tp_format is a libtraceevent type so this patch makes the variable > conditional on HAVE_LIBTRACEEVENT. I think this will remain true even > with a new evsel__newtp function that isn't dependent on > libtraceevent. I also think adding such things is best kept out of > this patch which is trying to do the minimal (only 312 lines of > addition) to have a build without libtraceevent. > > Given we expect builds to use libtraceevent and we should build off of > this patch, I think we should look to land it for 6.2.
So I took a quick look and it seems not quite easy to isolate libtraceevent accesses from perf trace, dynamic sort keys and other places. That would need some amount of work.
Now I think that we may apply this first and then work on enabling more functionalities without libtraceevent gradually.
Also I think it'd be a major change for regular users if there's no libtraceevent installed in their system. Maybe we could add a warning during the build?
Thanks, Namhyung
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