Re: [PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs

From: Arnaldo Carvalho de Melo
Date: Fri Feb 15 2019 - 09:41:58 EST

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In reply to: Song Liu: "[PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs"
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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@xxxxxx>
> ---
> 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;

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?

- 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

Next message: Christoph Hellwig: "allow larger than require DMA masks"
Previous message: Claudiu Manoil: "RE: [PATCH net-next v2 3/3] enetc: Add ENETC PF level external MDIO support"
In reply to: Song Liu: "[PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs"
Next in thread: Song Liu: "Re: [PATCH v2 perf,bpf 11/11] perf, bpf: save information about short living bpf programs"
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