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SubjectRe: [PATCH v2 perf,bpf 08/11] perf, bpf: save btf information as headers to perf.data
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> On Feb 15, 2019, at 6:26 AM, Arnaldo Carvalho de Melo <acme@redhat.com> wrote:
>
> Em Thu, Feb 14, 2019 at 04:00:09PM -0800, Song Liu escreveu:
>> This patch enables perf-record to save btf information as headers to
>> perf.data A new header type HEADER_BTF is introduced for this data.
>
> Jiri,
>
> Wouldn't it be better for this HEADER_BTF to be introduced
> already as an user space event, Song, see:
>
> tools/perf/util/event.h
>
> and:
>
> tools/perf/util/event.c
>
> perf_event__synthesize_cpu_map()
>
> - Arnaldo
>

BTF would be short living for short living BPF programs. I guess
saving them as header is easier than merging them with samples.

What's the benefit of saving them as user space events?

Thanks,
Song


>
>> Signed-off-by: Song Liu <songliubraving@fb.com>
>> ---
>> tools/perf/util/header.c | 99 +++++++++++++++++++++++++++++++++++++++-
>> tools/perf/util/header.h | 1 +
>> 2 files changed, 99 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
>> index 2ae76a9d06f6..3f1562afe8e5 100644
>> --- a/tools/perf/util/header.c
>> +++ b/tools/perf/util/header.c
>> @@ -1125,6 +1125,45 @@ static int write_bpf_prog_info(struct feat_fd *ff,
>> return ret;
>> }
>>
>> +static int write_btf(struct feat_fd *ff,
>> + struct perf_evlist *evlist __maybe_unused)
>> +{
>> + struct perf_env *env = &ff->ph->env;
>> + struct rb_root *root;
>> + struct rb_node *next;
>> + u32 count = 0;
>> + int ret;
>> +
>> + down_read(&env->bpf_info_lock);
>> +
>> + root = &env->btfs;
>> + next = rb_first(root);
>> + while (next) {
>> + ++count;
>> + next = rb_next(next);
>> + }
>> +
>> + ret = do_write(ff, &count, sizeof(count));
>> +
>> + if (ret < 0)
>> + goto out;
>> +
>> + next = rb_first(root);
>> + while (next) {
>> + struct btf_node *node;
>> +
>> + node = rb_entry(next, struct btf_node, rb_node);
>> + next = rb_next(&node->rb_node);
>> + ret = do_write(ff, node,
>> + sizeof(struct btf_node) + node->data_size);
>> + if (ret < 0)
>> + goto out;
>> + }
>> +out:
>> + up_read(&env->bpf_info_lock);
>> + return ret;
>> +}
>> +
>> static int cpu_cache_level__sort(const void *a, const void *b)
>> {
>> struct cpu_cache_level *cache_a = (struct cpu_cache_level *)a;
>> @@ -1628,6 +1667,28 @@ static void print_bpf_prog_info(struct feat_fd *ff, FILE *fp)
>> up_read(&env->bpf_info_lock);
>> }
>>
>> +static void print_btf(struct feat_fd *ff, FILE *fp)
>> +{
>> + struct perf_env *env = &ff->ph->env;
>> + struct rb_root *root;
>> + struct rb_node *next;
>> +
>> + down_read(&env->bpf_info_lock);
>> +
>> + root = &env->btfs;
>> + next = rb_first(root);
>> +
>> + while (next) {
>> + struct btf_node *node;
>> +
>> + node = rb_entry(next, struct btf_node, rb_node);
>> + next = rb_next(&node->rb_node);
>> + fprintf(fp, "# bpf_prog_info of id %u\n", node->id);
>> + }
>> +
>> + up_read(&env->bpf_info_lock);
>> +}
>> +
>> static void free_event_desc(struct perf_evsel *events)
>> {
>> struct perf_evsel *evsel;
>> @@ -2723,6 +2784,41 @@ static int process_bpf_prog_info(struct feat_fd *ff,
>> return err;
>> }
>>
>> +static int process_btf(struct feat_fd *ff, void *data __maybe_unused)
>> +{
>> + struct perf_env *env = &ff->ph->env;
>> + u32 count, i;
>> +
>> + if (do_read_u32(ff, &count))
>> + return -1;
>> +
>> + down_write(&env->bpf_info_lock);
>> +
>> + for (i = 0; i < count; ++i) {
>> + struct btf_node btf_node;
>> + struct btf_node *node;
>> +
>> + if (__do_read(ff, &btf_node, sizeof(struct btf_node)))
>> + return -1;
>> +
>> + node = malloc(sizeof(struct btf_node) + btf_node.data_size);
>> + if (!node)
>> + return -1;
>> +
>> + node->id = btf_node.id;
>> + node->data_size = btf_node.data_size;
>> +
>> + if (__do_read(ff, node->data, btf_node.data_size)) {
>> + free(node);
>> + return -1;
>> + }
>> + perf_env__insert_btf(env, node);
>> + }
>> +
>> + up_write(&env->bpf_info_lock);
>> + return 0;
>> +}
>> +
>> struct feature_ops {
>> int (*write)(struct feat_fd *ff, struct perf_evlist *evlist);
>> void (*print)(struct feat_fd *ff, FILE *fp);
>> @@ -2783,7 +2879,8 @@ static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
>> FEAT_OPR(SAMPLE_TIME, sample_time, false),
>> FEAT_OPR(MEM_TOPOLOGY, mem_topology, true),
>> FEAT_OPR(CLOCKID, clockid, false),
>> - FEAT_OPR(BPF_PROG_INFO, bpf_prog_info, false)
>> + FEAT_OPR(BPF_PROG_INFO, bpf_prog_info, false),
>> + FEAT_OPR(BTF, btf, false)
>> };
>>
>> struct header_print_data {
>> diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
>> index 0785c91b4c3a..ba51d8e43c53 100644
>> --- a/tools/perf/util/header.h
>> +++ b/tools/perf/util/header.h
>> @@ -40,6 +40,7 @@ enum {
>> HEADER_MEM_TOPOLOGY,
>> HEADER_CLOCKID,
>> HEADER_BPF_PROG_INFO,
>> + HEADER_BTF,
>> HEADER_LAST_FEATURE,
>> HEADER_FEAT_BITS = 256,
>> };
>> --
>> 2.17.1

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