perf evlist: Introduce side band thread

This patch introduces side band thread that captures extended
information for events like PERF_RECORD_BPF_EVENT.

This new thread uses its own evlist that uses ring buffer with very low
watermark for lower latency.

To use side band thread, we need to:

1. add side band event(s) by calling perf_evlist__add_sb_event();
2. calls perf_evlist__start_sb_thread();
3. at the end of perf run, perf_evlist__stop_sb_thread().

In the next patch, we use this thread to handle PERF_RECORD_BPF_EVENT.

Committer notes:

Add fix by Jiri Olsa for when te sb_tread can't get started and then at
the end the stop_sb_thread() segfaults when joining the (non-existing)
thread.

That can happen when running 'perf top' or 'perf record' as a normal
user, for instance.

Further checks need to be done on top of this to more graciously handle
these possible failure scenarios.

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Link: http://lkml.kernel.org/r/20190312053051.2690567-15-songliubraving@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e79facc..6f645fd 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1137,6 +1137,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
        struct perf_data *data = &rec->data;
        struct perf_session *session;
        bool disabled = false, draining = false;
+       struct perf_evlist *sb_evlist = NULL;
        int fd;
 
        atexit(record__sig_exit);
@@ -1237,6 +1238,11 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
                goto out_child;
        }
 
+       if (perf_evlist__start_sb_thread(sb_evlist, &rec->opts.target)) {
+               pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n");
+               opts->no_bpf_event = true;
+       }
+
        err = record__synthesize(rec, false);
        if (err < 0)
                goto out_child;
@@ -1487,6 +1493,9 @@ out_child:
 
 out_delete_session:
        perf_session__delete(session);
+
+       if (!opts->no_bpf_event)
+               perf_evlist__stop_sb_thread(sb_evlist);
        return status;
 }
 

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index c2ea22c..3ce8a8d 100644 (file)
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1501,6 +1501,7 @@ int cmd_top(int argc, const char **argv)
                        "number of thread to run event synthesize"),
        OPT_END()
        };
+       struct perf_evlist *sb_evlist = NULL;
        const char * const top_usage[] = {
                "perf top [<options>]",
                NULL
@@ -1636,8 +1637,16 @@ int cmd_top(int argc, const char **argv)
                goto out_delete_evlist;
        }
 
+       if (perf_evlist__start_sb_thread(sb_evlist, target)) {
+               pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n");
+               opts->no_bpf_event = true;
+       }
+
        status = __cmd_top(&top);
 
+       if (!opts->no_bpf_event)
+               perf_evlist__stop_sb_thread(sb_evlist);
+
 out_delete_evlist:
        perf_evlist__delete(top.evlist);
        perf_session__delete(top.session);

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index ed20f43..ec78e93 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -19,6 +19,7 @@
 #include "debug.h"
 #include "units.h"
 #include "asm/bug.h"
+#include "bpf-event.h"
 #include <signal.h>
 #include <unistd.h>
 
@@ -1856,3 +1857,121 @@ struct perf_evsel *perf_evlist__reset_weak_group(struct perf_evlist *evsel_list,
        }
        return leader;
 }
+
+int perf_evlist__add_sb_event(struct perf_evlist **evlist,
+                             struct perf_event_attr *attr,
+                             perf_evsel__sb_cb_t cb,
+                             void *data)
+{
+       struct perf_evsel *evsel;
+       bool new_evlist = (*evlist) == NULL;
+
+       if (*evlist == NULL)
+               *evlist = perf_evlist__new();
+       if (*evlist == NULL)
+               return -1;
+
+       if (!attr->sample_id_all) {
+               pr_warning("enabling sample_id_all for all side band events\n");
+               attr->sample_id_all = 1;
+       }
+
+       evsel = perf_evsel__new_idx(attr, (*evlist)->nr_entries);
+       if (!evsel)
+               goto out_err;
+
+       evsel->side_band.cb = cb;
+       evsel->side_band.data = data;
+       perf_evlist__add(*evlist, evsel);
+       return 0;
+
+out_err:
+       if (new_evlist) {
+               perf_evlist__delete(*evlist);
+               *evlist = NULL;
+       }
+       return -1;
+}
+
+static void *perf_evlist__poll_thread(void *arg)
+{
+       struct perf_evlist *evlist = arg;
+       bool draining = false;
+       int i;
+
+       while (draining || !(evlist->thread.done)) {
+               if (draining)
+                       draining = false;
+               else if (evlist->thread.done)
+                       draining = true;
+
+               if (!draining)
+                       perf_evlist__poll(evlist, 1000);
+
+               for (i = 0; i < evlist->nr_mmaps; i++) {
+                       struct perf_mmap *map = &evlist->mmap[i];
+                       union perf_event *event;
+
+                       if (perf_mmap__read_init(map))
+                               continue;
+                       while ((event = perf_mmap__read_event(map)) != NULL) {
+                               struct perf_evsel *evsel = perf_evlist__event2evsel(evlist, event);
+
+                               if (evsel && evsel->side_band.cb)
+                                       evsel->side_band.cb(event, evsel->side_band.data);
+                               else
+                                       pr_warning("cannot locate proper evsel for the side band event\n");
+
+                               perf_mmap__consume(map);
+                       }
+                       perf_mmap__read_done(map);
+               }
+       }
+       return NULL;
+}
+
+int perf_evlist__start_sb_thread(struct perf_evlist *evlist,
+                                struct target *target)
+{
+       struct perf_evsel *counter;
+
+       if (!evlist)
+               return 0;
+
+       if (perf_evlist__create_maps(evlist, target))
+               goto out_delete_evlist;
+
+       evlist__for_each_entry(evlist, counter) {
+               if (perf_evsel__open(counter, evlist->cpus,
+                                    evlist->threads) < 0)
+                       goto out_delete_evlist;
+       }
+
+       if (perf_evlist__mmap(evlist, UINT_MAX))
+               goto out_delete_evlist;
+
+       evlist__for_each_entry(evlist, counter) {
+               if (perf_evsel__enable(counter))
+                       goto out_delete_evlist;
+       }
+
+       evlist->thread.done = 0;
+       if (pthread_create(&evlist->thread.th, NULL, perf_evlist__poll_thread, evlist))
+               goto out_delete_evlist;
+
+       return 0;
+
+out_delete_evlist:
+       perf_evlist__delete(evlist);
+       evlist = NULL;
+       return -1;
+}
+
+void perf_evlist__stop_sb_thread(struct perf_evlist *evlist)
+{
+       if (!evlist)
+               return;
+       evlist->thread.done = 1;
+       pthread_join(evlist->thread.th, NULL);
+       perf_evlist__delete(evlist);
+}

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 744906d..dcb68f3 100644 (file)
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -54,6 +54,10 @@ struct perf_evlist {
                                       struct perf_sample *sample);
        u64             first_sample_time;
        u64             last_sample_time;
+       struct {
+               pthread_t               th;
+               volatile int            done;
+       } thread;
 };
 
 struct perf_evsel_str_handler {
@@ -87,6 +91,14 @@ int __perf_evlist__add_default_attrs(struct perf_evlist *evlist,
 
 int perf_evlist__add_dummy(struct perf_evlist *evlist);
 
+int perf_evlist__add_sb_event(struct perf_evlist **evlist,
+                             struct perf_event_attr *attr,
+                             perf_evsel__sb_cb_t cb,
+                             void *data);
+int perf_evlist__start_sb_thread(struct perf_evlist *evlist,
+                                struct target *target);
+void perf_evlist__stop_sb_thread(struct perf_evlist *evlist);
+
 int perf_evlist__add_newtp(struct perf_evlist *evlist,
                           const char *sys, const char *name, void *handler);
 

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index cc578e0..0f2c6c9 100644 (file)
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -73,6 +73,8 @@ struct perf_evsel_config_term {
 
 struct perf_stat_evsel;
 
+typedef int (perf_evsel__sb_cb_t)(union perf_event *event, void *data);
+
 /** struct perf_evsel - event selector
  *
  * @evlist - evlist this evsel is in, if it is in one.
@@ -151,6 +153,10 @@ struct perf_evsel {
        bool                    collect_stat;
        bool                    weak_group;
        const char              *pmu_name;
+       struct {
+               perf_evsel__sb_cb_t     *cb;
+               void                    *data;
+       } side_band;
 };
 
 union u64_swap {