Messages in this thread | | | From | Namhyung Kim <> | Subject | Re: [PATCH 02/12] perf header: Add HEADER_GROUP_DESC feature | Date | Tue, 13 Nov 2012 10:51:14 +0900 |
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On Mon, 12 Nov 2012 14:45:34 -0300, Arnaldo Carvalho de Melo wrote: > Em Sat, Nov 10, 2012 at 01:43:24AM +0900, Namhyung Kim escreveu: >> From: Namhyung Kim <namhyung.kim@lge.com> >> >> Save group relationship information so that it can be restored when >> perf report is running. >> >> Cc: Jiri Olsa <jolsa@redhat.com> >> Cc: Stephane Eranian <eranian@google.com> >> Acked-by: Jiri Olsa <jolsa@redhat.com> >> Signed-off-by: Namhyung Kim <namhyung@kernel.org> > > <SNIP> > >> +static int process_group_desc(struct perf_file_section *section __maybe_unused, >> + struct perf_header *ph, int fd, >> + void *data __maybe_unused) >> +{ >> + size_t ret = -1; > > why initialize ret if the first thing you do with it is... > >> + u32 i, nr, nr_groups; >> + struct perf_session *session; >> + struct perf_evsel *evsel, *leader = NULL; >> + struct group_desc { >> + char *name; >> + u32 leader_idx; >> + u32 nr_members; >> + } *desc; >> + >> + ret = read(fd, &nr_groups, sizeof(nr_groups)); > > assign another value? > > We need to use readn instead of read, and not use ret here, just do > if (read(fd, &nr_groups, sizeof(nr_groups)) != sizeof(nr_groups))
Will do.
> >> + if (ret != sizeof(nr_groups)) >> + return -1; >> + >> + if (ph->needs_swap) >> + nr_groups = bswap_32(nr_groups); >> + >> + ph->env.nr_groups = nr_groups; >> + if (!nr_groups) { >> + pr_debug("group desc not available\n"); >> + return 0; >> + } >> + >> + desc = calloc(nr_groups, sizeof(*desc)); >> + if (!desc) >> + return -1; >> + >> + for (i = 0; i < nr_groups; i++) { >> + desc[i].name = do_read_string(fd, ph); >> + if (!desc[i].name) >> + goto out_free; >> + >> + ret = read(fd, &desc[i].leader_idx, sizeof(u32)); >> + if (ret != sizeof(u32)) >> + goto out_free; > > ditto > >> + >> + ret = read(fd, &desc[i].nr_members, sizeof(u32)); >> + if (ret != sizeof(u32)) >> + goto out_free; > > ditto > >> + >> + if (ph->needs_swap) { >> + desc[i].leader_idx = bswap_32(desc[i].leader_idx); >> + desc[i].nr_members = bswap_32(desc[i].nr_members); >> + } >> + } >> + >> + /* >> + * Rebuild group relationship based on the group_desc >> + */ >> + session = container_of(ph, struct perf_session, header); >> + session->evlist->nr_groups = nr_groups; >> + >> + i = nr = 0; >> + list_for_each_entry(evsel, &session->evlist->entries, node) { >> + if (evsel->idx == (int) desc[i].leader_idx) { >> + evsel->leader = NULL; > > Humm, isn't it better to set evsel->leader to evsel, that way all > members in a group have its evsel->leader pointing to the leader and for > things like the group idx we can do just: > > evsel->idx - evsel->leader->idx > > avoiding the need to special case the leader, will do that.
I just followed the existing behavior. I'm open to changing it. :)
> >> + /* {anon_group} is a dummy name */ >> + if (strcmp(desc[i].name, "{anon_group}")) >> + evsel->group_name = desc[i].name; >> + evsel->nr_members = desc[i].nr_members; >> + >> + BUG_ON(i >= nr_groups); >> + BUG_ON(nr > 0); > > BUG_ON here is way too extreme, we should just bail out, testing and if > the problem is found, goto out_free
Okay, it was there to help me debugging the code. Will change.
> >> + leader = evsel; >> + nr = evsel->nr_members; >> + i++; >> + } else if (nr) { > > Humm, do we really need to test against nr? Or even use nr at all?
The group descriptor misses leader-only groups intentionally. In that case I wanted to skip those events with nr == 0.
> >> + /* This is a group member */ >> + evsel->leader = leader; >> + /* group_idx starts from 0 */ >> + evsel->group_idx = leader->nr_members - nr; >> + nr--; >> + } >> + } >> + >> + BUG_ON(i != nr_groups); >> + BUG_ON(nr != 0); > > Too extreme, goto out_free. > > And just before out_free we need to set ret = 0, otherwise we will > return...
Right, will do.
> >> +out_free: >> + while ((int) --i >= 0) >> + free(desc[i].name); >> + free(desc); > > here, whatever value was in ret, in this patch it will be, if all goes > well, sizeof(u32) :-) > >> + return ret; >> +} >> + >> struct feature_ops { >> int (*write)(int fd, struct perf_header *h, struct perf_evlist *evlist); >> void (*print)(struct perf_header *h, int fd, FILE *fp); >> @@ -1986,6 +2137,7 @@ static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = { >> FEAT_OPF(HEADER_NUMA_TOPOLOGY, numa_topology), >> FEAT_OPA(HEADER_BRANCH_STACK, branch_stack), >> FEAT_OPP(HEADER_PMU_MAPPINGS, pmu_mappings), >> + FEAT_OPP(HEADER_GROUP_DESC, group_desc), >> }; >> >> struct header_print_data { >> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h >> index 5f1cd6884f37..e3e7fb490310 100644 >> --- a/tools/perf/util/header.h >> +++ b/tools/perf/util/header.h >> @@ -29,6 +29,7 @@ enum { >> HEADER_NUMA_TOPOLOGY, >> HEADER_BRANCH_STACK, >> HEADER_PMU_MAPPINGS, >> + HEADER_GROUP_DESC, >> HEADER_LAST_FEATURE, >> HEADER_FEAT_BITS = 256, >> }; > > Here we're adding holes to the struct: > >> @@ -79,6 +80,7 @@ struct perf_session_env { >> char *numa_nodes; >> int nr_pmu_mappings; > > 4 byte hole > >> char *pmu_mappings; > > 4 byte hole
Yes, I thought it's a in-memory struct for a session, so a couple of holes doesn't matter much. So I just wanted to keep the struct in a consistent and straight-forward way.
> >> + int nr_groups; > > I'm working on a patch implementing my suggestions.
Great!
Thanks, Namhyung
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