On Mon, Jul 24, 2017 at 04:40:04PM -0700, Andi Kleen wrote: > From: Andi Kleen <[email protected]> > > Setting up groups can be complicated due to the > complicated scheduling restrictions of different PMUs. > User tools usually don't understand all these restrictions. > Still in many cases it is useful to set up groups and > they work most of the time. However if the group > is set up wrong some members will not reported any values > because they never get scheduled. > > Add a concept of a 'weak group': try to set up a group, > but if it's not schedulable fallback to not using > a group. That gives us the best of both worlds: > groups if they work, but still a usable fallback if they don't. > > In theory it would be possible to have more complex fallback > strategies (e.g. try to split the group in half), but > the simple fallback of not using a group seems to work for now. > > So far the weak group is only implemented for perf stat, > not for record. > > Here's an unschedulable group (on IvyBridge with SMT on) > > % perf stat -e > '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}' > -a sleep 1 > > 73,806,067 branches > 4,848,144 branch-misses # 6.57% of all branches > 14,754,458 l1d.replacement > 24,905,558 l2_lines_in.all > <not supported> l2_rqsts.all_code_rd <------- will never > report anything > > With the weak group: > > % perf stat -e > '{branches,branch-misses,l1d.replacement,l2_lines_in.all,l2_rqsts.all_code_rd}:W' > -a sleep 1 > > 125,366,055 branches > (80.02%) > 9,208,402 branch-misses # 7.35% of all branches > (80.01%) > 24,560,249 l1d.replacement > (80.00%) > 43,174,971 l2_lines_in.all > (80.05%) > 31,891,457 l2_rqsts.all_code_rd > (79.92%)
looks handy, few comments below thanks, jirka > > The extra event scheduled with some extra multiplexing > > Signed-off-by: Andi Kleen <[email protected]> > --- SNIP > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index 97d6b6c42014..551ed938e05c 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -564,7 +564,7 @@ static int __run_perf_stat(int argc, const char **argv) > int interval = stat_config.interval; > char msg[BUFSIZ]; > unsigned long long t0, t1; > - struct perf_evsel *counter; > + struct perf_evsel *counter, *c2, *leader; > struct timespec ts; > size_t l; > int status = 0; > @@ -595,6 +595,32 @@ static int __run_perf_stat(int argc, const char **argv) > evlist__for_each_entry(evsel_list, counter) { > try_again: > if (create_perf_stat_counter(counter) < 0) { > + /* Weak group failed. Reset the group. */ > + if (errno == EINVAL && > + counter->leader != counter && > + counter->weak_group) { could you please put this de-grouping code into a function? > + bool is_open = true; > + > + pr_debug("Weak group for %s/%d failed\n", > + counter->leader->name, > counter->nr_members); > + leader = counter->leader; > + evlist__for_each_entry(evsel_list, c2) { we have for_each_group_member > + if (c2 == counter) > + is_open = false; > + if (c2->leader == leader) { > + if (is_open) > + perf_evsel__close(c2, > + c2->cpus ? > c2->cpus->nr : > + > cpu_map__nr(evsel_list->cpus), > + > thread_map__nr(evsel_list->threads)); > + c2->leader = c2; > + c2->nr_members = 0; > + } > + } > + counter = leader; > + goto try_again; > + } > + > /* > * PPC returns ENXIO for HW counters until 2.6.37 > * (behavior changed with commit b0a873e). SNIP
