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    SubjectRe: [PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs
    Em Fri, Feb 15, 2019 at 05:13:01PM +0000, Song Liu escreveu:
    > > On Feb 15, 2019, at 6:41 AM, Arnaldo Carvalho de Melo <acme@redhat.com> wrote:
    > > Em Thu, Feb 14, 2019 at 04:00:45PM -0800, Song Liu escreveu:
    > >> +pthread_t poll_thread;
    > >> +
    > >> +int bpf_event__start_polling_thread(struct bpf_event_poll_args *args)
    > >> +{
    > >> + struct perf_evsel *counter;
    > >> +
    > >> + args->evlist = perf_evlist__new();
    > >> +
    > >> + if (args->evlist == NULL)
    > >> + return -1;
    > >> +
    > >> + if (perf_evlist__create_maps(args->evlist, args->target))
    > > goto out_delete_evlist;
    > >> +
    > >> + if (perf_evlist__add_bpf_tracker(args->evlist))
    > > goto out_delete_evlist;
    > >> +
    > >> + evlist__for_each_entry(args->evlist, counter) {
    > >> + if (perf_evsel__open(counter, args->evlist->cpus,
    > >> + args->evlist->threads) < 0)
    > > goto out_delete_evlist;
    > >> + }
    > >> +
    > >> + if (perf_evlist__mmap(args->evlist, UINT_MAX))
    > > goto out_delete_evlist;
    > >> +
    > >> + evlist__for_each_entry(args->evlist, counter) {
    > >> + if (perf_evsel__enable(counter))
    > > goto out_delete_evlist;
    > >> + }
    > >> +
    > >> + if (pthread_create(&poll_thread, NULL, bpf_poll_thread, args))
    > > goto out_delete_evlist;
    > >> +
    > >> + return 0;
    > > out_delete_evlist:
    > > perf_evlist__delete(args->evlist);
    > > args->evlist = NULL;

    Have you seen the error handling suggestion above?

    > >> +int perf_evlist__add_bpf_tracker(struct perf_evlist *evlist)
    > >> +{
    > >> + struct perf_event_attr attr = {
    > >> + .type = PERF_TYPE_SOFTWARE,
    > >> + .config = PERF_COUNT_SW_DUMMY,
    > >> + .watermark = 1,
    > >> + .bpf_event = 1,
    > >> + .wakeup_watermark = 1,
    > >> + .size = sizeof(attr), /* to capture ABI version */
    > >> + };
    > >> + struct perf_evsel *evsel = perf_evsel__new_idx(&attr,
    > >> + evlist->nr_entries);
    > >> +
    > >> + if (evsel == NULL)
    > >> + return -ENOMEM;
    > >> +
    > >> + perf_evlist__add(evlist, evsel);

    > > You could use:

    > > struct perf_evlist *evlist = perf_evlist__new_dummy();
    > > if (evlist != NULL) {
    > > struct perf_evsel *evsel == perf_evlist__first(evlist);
    > > evsel->attr.bpf_event = evsel->attr.watermark = evsel->attr.wakeup_watermark = 1;
    > > return 0;
    > > }
    > > return -1;

    > This looks cleaner. Let me fix in next version.

    > > Because in this case all you'll have in this evlist is the bpf tracker,
    > > right? The add_bpf_tracker would be handy if we would want to have a
    > > pre-existing evlist with some other events and wanted to add a bpf
    > > tracker, no?

    > I think all we need is a side-band evlist instead of the main evlist. May
    > be we should call it side-band evlist, and make it more generic?

    Sure, you could for instance have something like:

    struct perf_event_attr attr = {
    .watermark = 1,
    .bpf_event = 1,
    .wakeup_watermark = 1,
    }
    struct perf_evlist *evlist = perf_evlist__new_side_band(&attr);


    And the other details will be set by it, i.e. the .config

    .type = PERF_TYPE_SOFTWARE,
    .config = PERF_COUNT_SW_DUMMY,
    .size = sizeof(attr), /* to capture ABI version */

    And the idx arg.

    - Arnaldo

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