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SubjectRe: [PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs
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> 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:
>> To annotate bpf programs in perf, it is necessary to save information in
>> bpf_prog_info and btf. For short living bpf program, it is necessary to
>> save these information before it is unloaded.
>>
>> This patch saves these information in a separate thread. This thread
>> creates its own evlist, that only tracks bpf events. This evlists uses
>> ring buffer with very low watermark for lower latency. When bpf load
>> events are received, this thread tries to gather information via sys_bpf
>> and save it in perf_env.
>>
>> Signed-off-by: Song Liu <songliubraving@fb.com>
>> ---
>> tools/perf/builtin-record.c | 13 ++++
>> tools/perf/builtin-top.c | 12 ++++
>> tools/perf/util/bpf-event.c | 129 ++++++++++++++++++++++++++++++++++++
>> tools/perf/util/bpf-event.h | 22 ++++++
>> tools/perf/util/evlist.c | 20 ++++++
>> tools/perf/util/evlist.h | 2 +
>> 6 files changed, 198 insertions(+)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index 2355e0a9eda0..46abb44aaaab 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -1106,6 +1106,8 @@ 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 bpf_event_poll_args poll_args;
>> + bool bpf_thread_running = false;
>> int fd;
>>
>> atexit(record__sig_exit);
>> @@ -1206,6 +1208,14 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>> goto out_child;
>> }
>>
>> + if (rec->opts.bpf_event) {
>> + poll_args.env = &session->header.env;
>> + poll_args.target = &rec->opts.target;
>> + poll_args.done = &done;
>> + if (bpf_event__start_polling_thread(&poll_args) == 0)
>> + bpf_thread_running = true;
>> + }
>> +
>> err = record__synthesize(rec, false);
>> if (err < 0)
>> goto out_child;
>> @@ -1456,6 +1466,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>
>> out_delete_session:
>> perf_session__delete(session);
>> +
>> + if (bpf_thread_running)
>> + bpf_event__stop_polling_thread(&poll_args);
>> return status;
>> }
>>
>> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
>> index 5271d7211b9c..2586ee081967 100644
>> --- a/tools/perf/builtin-top.c
>> +++ b/tools/perf/builtin-top.c
>> @@ -1524,10 +1524,12 @@ int cmd_top(int argc, const char **argv)
>> "number of thread to run event synthesize"),
>> OPT_END()
>> };
>> + struct bpf_event_poll_args poll_args;
>> const char * const top_usage[] = {
>> "perf top [<options>]",
>> NULL
>> };
>> + bool bpf_thread_running = false;
>> int status = hists__init();
>>
>> if (status < 0)
>> @@ -1652,8 +1654,18 @@ int cmd_top(int argc, const char **argv)
>> signal(SIGWINCH, winch_sig);
>> }
>>
>> + if (top.record_opts.bpf_event) {
>> + poll_args.env = &perf_env;
>> + poll_args.target = target;
>> + poll_args.done = &done;
>> + if (bpf_event__start_polling_thread(&poll_args) == 0)
>> + bpf_thread_running = true;
>> + }
>> status = __cmd_top(&top);
>>
>> + if (bpf_thread_running)
>> + bpf_event__stop_polling_thread(&poll_args);
>> +
>> out_delete_evlist:
>> perf_evlist__delete(top.evlist);
>>
>> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
>> index 4f347d61ed96..0caf137c515b 100644
>> --- a/tools/perf/util/bpf-event.c
>> +++ b/tools/perf/util/bpf-event.c
>> @@ -8,6 +8,7 @@
>> #include "machine.h"
>> #include "env.h"
>> #include "session.h"
>> +#include "evlist.h"
>>
>> #define ptr_to_u64(ptr) ((__u64)(unsigned long)(ptr))
>>
>> @@ -316,3 +317,131 @@ int perf_event__synthesize_bpf_events(struct perf_session *session,
>> free(event);
>> return err;
>> }
>> +
>> +static void perf_env_add_bpf_info(struct perf_env *env, u32 id)
>> +{
>> + struct bpf_prog_info_linear *info_linear;
>> + struct bpf_prog_info_node *info_node;
>> + struct btf *btf = NULL;
>> + u64 arrays;
>> + u32 btf_id;
>> + int fd;
>> +
>> + fd = bpf_prog_get_fd_by_id(id);
>> + if (fd < 0)
>> + return;
>> +
>> + arrays = 1UL << BPF_PROG_INFO_JITED_KSYMS;
>> + arrays |= 1UL << BPF_PROG_INFO_JITED_FUNC_LENS;
>> + arrays |= 1UL << BPF_PROG_INFO_FUNC_INFO;
>> + arrays |= 1UL << BPF_PROG_INFO_PROG_TAGS;
>> + arrays |= 1UL << BPF_PROG_INFO_JITED_INSNS;
>> + arrays |= 1UL << BPF_PROG_INFO_LINE_INFO;
>> + arrays |= 1UL << BPF_PROG_INFO_JITED_LINE_INFO;
>> +
>> + info_linear = bpf_program__get_prog_info_linear(fd, arrays);
>> + if (IS_ERR_OR_NULL(info_linear)) {
>> + pr_debug("%s: failed to get BPF program info. aborting\n", __func__);
>> + goto out;
>> + }
>> +
>> + btf_id = info_linear->info.btf_id;
>> +
>> + info_node = malloc(sizeof(struct bpf_prog_info_node));
>> + if (info_node) {
>> + info_node->info_linear = info_linear;
>> + perf_env__insert_bpf_prog_info(env, info_node);
>> + } else
>> + free(info_linear);
>> +
>> + if (btf_id == 0)
>> + goto out;
>> +
>> + if (btf__get_from_id(btf_id, &btf)) {
>> + pr_debug("%s: failed to get BTF of id %u, aborting\n",
>> + __func__, btf_id);
>> + goto out;
>> + }
>> + perf_fetch_btf(env, btf_id, btf);
>> +
>> +out:
>> + free(btf);
>> + close(fd);
>> +}
>> +
>> +static void *bpf_poll_thread(void *arg)
>> +{
>> + struct bpf_event_poll_args *args = arg;
>> + int i;
>> +
>> + while (!*(args->done)) {
>> + perf_evlist__poll(args->evlist, 1000);
>> +
>> + for (i = 0; i < args->evlist->nr_mmaps; i++) {
>> + struct perf_mmap *map = &args->evlist->mmap[i];
>> + union perf_event *event;
>> +
>> + if (perf_mmap__read_init(map))
>> + continue;
>> + while ((event = perf_mmap__read_event(map)) != NULL) {
>> + pr_debug("processing vip event of type %d\n",
>> + event->header.type);
>> + switch (event->header.type) {
>> + case PERF_RECORD_BPF_EVENT:
>> + if (event->bpf_event.type != PERF_BPF_EVENT_PROG_LOAD)
>> + break;
>> + perf_env_add_bpf_info(args->env, event->bpf_event.id);
>> + break;
>> + default:
>> + break;
>> + }
>> + perf_mmap__consume(map);
>> + }
>> + perf_mmap__read_done(map);
>> + }
>> + }
>> + return NULL;
>> +}
>> +
>> +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;
>
> return -1;
>> +}
>> +
>> +void bpf_event__stop_polling_thread(struct bpf_event_poll_args *args)
>> +{
>> + pthread_join(poll_thread, NULL);
>> + perf_evlist__exit(args->evlist);
>> +}
>> diff --git a/tools/perf/util/bpf-event.h b/tools/perf/util/bpf-event.h
>> index c4f0f1395ea5..61914827c1e3 100644
>> --- a/tools/perf/util/bpf-event.h
>> +++ b/tools/perf/util/bpf-event.h
>> @@ -12,12 +12,17 @@
>> #include <bpf/libbpf.h>
>> #include <linux/btf.h>
>> #include <linux/rbtree.h>
>> +#include <pthread.h>
>> +#include <api/fd/array.h>
>> #include "event.h"
>>
>> struct machine;
>> union perf_event;
>> +struct perf_env;
>> struct perf_sample;
>> struct record_opts;
>> +struct evlist;
>> +struct target;
>>
>> struct bpf_prog_info_node {
>> struct bpf_prog_info_linear *info_linear;
>> @@ -31,6 +36,13 @@ struct btf_node {
>> char data[];
>> };
>>
>> +struct bpf_event_poll_args {
>> + struct perf_env *env;
>> + struct perf_evlist *evlist;
>> + struct target *target;
>> + volatile int *done;
>> +};
>> +
>> #ifdef HAVE_LIBBPF_SUPPORT
>> int machine__process_bpf_event(struct machine *machine, union perf_event *event,
>> struct perf_sample *sample);
>> @@ -39,6 +51,8 @@ int perf_event__synthesize_bpf_events(struct perf_session *session,
>> perf_event__handler_t process,
>> struct machine *machine,
>> struct record_opts *opts);
>> +int bpf_event__start_polling_thread(struct bpf_event_poll_args *args);
>> +void bpf_event__stop_polling_thread(struct bpf_event_poll_args *args);
>> #else
>> static inline int machine__process_bpf_event(struct machine *machine __maybe_unused,
>> union perf_event *event __maybe_unused,
>> @@ -54,5 +68,13 @@ static inline int perf_event__synthesize_bpf_events(struct perf_session *session
>> {
>> return 0;
>> }
>> +
>> +static inline int bpf_event__start_polling_thread(struct bpf_event_poll_args *args __maybe_unused)
>> +{
>> + return 0;
>> +}
>> +void bpf_event__stop_polling_thread(struct bpf_event_poll_args *args __maybe_unused)
>> +{
>> +}
>> #endif // HAVE_LIBBPF_SUPPORT
>> #endif
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index 8c902276d4b4..612c079579ce 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -271,6 +271,26 @@ int perf_evlist__add_dummy(struct perf_evlist *evlist)
>> return 0;
>> }
>>
>> +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?

Thanks,
Song

>
> - Arnaldo
>
>> + return 0;
>> +}
>> +
>> static int perf_evlist__add_attrs(struct perf_evlist *evlist,
>> struct perf_event_attr *attrs, size_t nr_attrs)
>> {
>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
>> index 868294491194..a2d22715188e 100644
>> --- a/tools/perf/util/evlist.h
>> +++ b/tools/perf/util/evlist.h
>> @@ -84,6 +84,8 @@ int __perf_evlist__add_default_attrs(struct perf_evlist *evlist,
>>
>> int perf_evlist__add_dummy(struct perf_evlist *evlist);
>>
>> +int perf_evlist__add_bpf_tracker(struct perf_evlist *evlist);
>> +
>> int perf_evlist__add_newtp(struct perf_evlist *evlist,
>> const char *sys, const char *name, void *handler);
>>
>> --
>> 2.17.1

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