perf bench: Add build-id injection benchmark

Sometimes I can see that 'perf record' piped with 'perf inject' take a
long time processing build-ids.

So introduce a inject-build-id benchmark to the internals benchmark
suite to measure its overhead regularly.

It runs the 'perf inject' command internally and feeds the given number
of synthesized events (MMAP2 + SAMPLE basically).

  Usage: perf bench internals inject-build-id <options>

    -i, --iterations <n>  Number of iterations used to compute average (default: 100)
    -m, --nr-mmaps <n>    Number of mmap events for each iteration (default: 100)
    -n, --nr-samples <n>  Number of sample events per mmap event (default: 100)
    -v, --verbose         be more verbose (show iteration count, DSO name, etc)

By default, it measures average processing time of 100 MMAP2 events
and 10000 SAMPLE events.  Below is a result on my laptop.

  $ perf bench internals inject-build-id
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 25.789 msec (+- 0.202 msec)
    Average time per event: 2.528 usec (+- 0.020 usec)
    Average memory usage: 8411 KB (+- 7 KB)

Committer testing:

  $ perf bench
  Usage:
  	perf bench [<common options>] <collection> <benchmark> [<options>]

          # List of all available benchmark collections:

           sched: Scheduler and IPC benchmarks
         syscall: System call benchmarks
             mem: Memory access benchmarks
            numa: NUMA scheduling and MM benchmarks
           futex: Futex stressing benchmarks
           epoll: Epoll stressing benchmarks
       internals: Perf-internals benchmarks
             all: All benchmarks

  $ perf bench internals

          # List of available benchmarks for collection 'internals':

      synthesize: Benchmark perf event synthesis
  kallsyms-parse: Benchmark kallsyms parsing
  inject-build-id: Benchmark build-id injection

  $ perf bench internals inject-build-id
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.202 msec (+- 0.059 msec)
    Average time per event: 1.392 usec (+- 0.006 usec)
    Average memory usage: 12650 KB (+- 10 KB)
    Average build-id-all injection took: 12.831 msec (+- 0.071 msec)
    Average time per event: 1.258 usec (+- 0.007 usec)
    Average memory usage: 11895 KB (+- 10 KB)
  $

  $ perf stat -r5 perf bench internals inject-build-id
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.380 msec (+- 0.056 msec)
    Average time per event: 1.410 usec (+- 0.006 usec)
    Average memory usage: 12608 KB (+- 11 KB)
    Average build-id-all injection took: 11.889 msec (+- 0.064 msec)
    Average time per event: 1.166 usec (+- 0.006 usec)
    Average memory usage: 11838 KB (+- 10 KB)
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.246 msec (+- 0.065 msec)
    Average time per event: 1.397 usec (+- 0.006 usec)
    Average memory usage: 12744 KB (+- 10 KB)
    Average build-id-all injection took: 12.019 msec (+- 0.066 msec)
    Average time per event: 1.178 usec (+- 0.006 usec)
    Average memory usage: 11963 KB (+- 10 KB)
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.321 msec (+- 0.067 msec)
    Average time per event: 1.404 usec (+- 0.007 usec)
    Average memory usage: 12690 KB (+- 10 KB)
    Average build-id-all injection took: 11.909 msec (+- 0.041 msec)
    Average time per event: 1.168 usec (+- 0.004 usec)
    Average memory usage: 11938 KB (+- 10 KB)
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.287 msec (+- 0.059 msec)
    Average time per event: 1.401 usec (+- 0.006 usec)
    Average memory usage: 12864 KB (+- 10 KB)
    Average build-id-all injection took: 11.862 msec (+- 0.058 msec)
    Average time per event: 1.163 usec (+- 0.006 usec)
    Average memory usage: 12103 KB (+- 10 KB)
  # Running 'internals/inject-build-id' benchmark:
    Average build-id injection took: 14.402 msec (+- 0.053 msec)
    Average time per event: 1.412 usec (+- 0.005 usec)
    Average memory usage: 12876 KB (+- 10 KB)
    Average build-id-all injection took: 11.826 msec (+- 0.061 msec)
    Average time per event: 1.159 usec (+- 0.006 usec)
    Average memory usage: 12111 KB (+- 10 KB)

   Performance counter stats for 'perf bench internals inject-build-id' (5 runs):

            4,267.48 msec task-clock:u              #    1.502 CPUs utilized            ( +-  0.14% )
                   0      context-switches:u        #    0.000 K/sec
                   0      cpu-migrations:u          #    0.000 K/sec
             102,092      page-faults:u             #    0.024 M/sec                    ( +-  0.08% )
       3,894,589,578      cycles:u                  #    0.913 GHz                      ( +-  0.19% )  (83.49%)
         140,078,421      stalled-cycles-frontend:u #    3.60% frontend cycles idle     ( +-  0.77% )  (83.34%)
         948,581,189      stalled-cycles-backend:u  #   24.36% backend cycles idle      ( +-  0.46% )  (83.25%)
       5,835,587,719      instructions:u            #    1.50  insn per cycle
                                                    #    0.16  stalled cycles per insn  ( +-  0.21% )  (83.24%)
       1,267,423,636      branches:u                #  296.996 M/sec                    ( +-  0.22% )  (83.12%)
          17,484,290      branch-misses:u           #    1.38% of all branches          ( +-  0.12% )  (83.55%)

             2.84176 +- 0.00222 seconds time elapsed  ( +-  0.08% )

  $

Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20201012070214.2074921-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

6 files changed, 471 insertions, 5 deletions

diff --git a/tools/perf/bench/Build b/tools/perf/bench/Build
index dd68a40a790c..8b52591338d6 100644
--- a/tools/perf/bench/Build
+++ b/tools/perf/bench/Build
@@ -12,6 +12,7 @@ perf-y += epoll-ctl.o
 perf-y += synthesize.o
 perf-y += kallsyms-parse.o
 perf-y += find-bit-bench.o
+perf-y += inject-buildid.o
 
 perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-lib.o
 perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h
index 2804812d4154..eac36afab2b3 100644
--- a/tools/perf/bench/bench.h
+++ b/tools/perf/bench/bench.h
@@ -47,6 +47,7 @@ int bench_epoll_wait(int argc, const char **argv);
 int bench_epoll_ctl(int argc, const char **argv);
 int bench_synthesize(int argc, const char **argv);
 int bench_kallsyms_parse(int argc, const char **argv);
+int bench_inject_build_id(int argc, const char **argv);
 
 #define BENCH_FORMAT_DEFAULT_STR	"default"
 #define BENCH_FORMAT_DEFAULT		0
diff --git a/tools/perf/bench/inject-buildid.c b/tools/perf/bench/inject-buildid.c
new file mode 100644
index 000000000000..0fccf2a9e95b
--- /dev/null
+++ b/tools/perf/bench/inject-buildid.c
@@ -0,0 +1,460 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdlib.h>
+#include <stddef.h>
+#include <ftw.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <linux/kernel.h>
+#include <linux/time64.h>
+#include <linux/list.h>
+#include <linux/err.h>
+#include <internal/lib.h>
+#include <subcmd/parse-options.h>
+
+#include "bench.h"
+#include "util/data.h"
+#include "util/stat.h"
+#include "util/debug.h"
+#include "util/event.h"
+#include "util/symbol.h"
+#include "util/session.h"
+#include "util/build-id.h"
+#include "util/synthetic-events.h"
+
+#define MMAP_DEV_MAJOR  8
+#define DSO_MMAP_RATIO  4
+
+static unsigned int iterations = 100;
+static unsigned int nr_mmaps   = 100;
+static unsigned int nr_samples = 100;  /* samples per mmap */
+
+static u64 bench_sample_type;
+static u16 bench_id_hdr_size;
+
+struct bench_data {
+	int			pid;
+	int			input_pipe[2];
+	int			output_pipe[2];
+	pthread_t		th;
+};
+
+struct bench_dso {
+	struct list_head	list;
+	char			*name;
+	int			ino;
+};
+
+static int nr_dsos;
+static struct bench_dso *dsos;
+
+extern int cmd_inject(int argc, const char *argv[]);
+
+static const struct option options[] = {
+	OPT_UINTEGER('i', "iterations", &iterations,
+		     "Number of iterations used to compute average (default: 100)"),
+	OPT_UINTEGER('m', "nr-mmaps", &nr_mmaps,
+		     "Number of mmap events for each iteration (default: 100)"),
+	OPT_UINTEGER('n', "nr-samples", &nr_samples,
+		     "Number of sample events per mmap event (default: 100)"),
+	OPT_INCR('v', "verbose", &verbose,
+		 "be more verbose (show iteration count, DSO name, etc)"),
+	OPT_END()
+};
+
+static const char *const bench_usage[] = {
+	"perf bench internals inject-build-id <options>",
+	NULL
+};
+
+/*
+ * Helper for collect_dso that adds the given file as a dso to dso_list
+ * if it contains a build-id.  Stops after collecting 4 times more than
+ * we need (for MMAP2 events).
+ */
+static int add_dso(const char *fpath, const struct stat *sb __maybe_unused,
+		   int typeflag, struct FTW *ftwbuf __maybe_unused)
+{
+	struct bench_dso *dso = &dsos[nr_dsos];
+	unsigned char build_id[BUILD_ID_SIZE];
+
+	if (typeflag == FTW_D || typeflag == FTW_SL)
+		return 0;
+
+	if (filename__read_build_id(fpath, build_id, BUILD_ID_SIZE) < 0)
+		return 0;
+
+	dso->name = realpath(fpath, NULL);
+	if (dso->name == NULL)
+		return -1;
+
+	dso->ino = nr_dsos++;
+	pr_debug2("  Adding DSO: %s\n", fpath);
+
+	/* stop if we collected enough DSOs */
+	if ((unsigned int)nr_dsos == DSO_MMAP_RATIO * nr_mmaps)
+		return 1;
+
+	return 0;
+}
+
+static void collect_dso(void)
+{
+	dsos = calloc(nr_mmaps * DSO_MMAP_RATIO, sizeof(*dsos));
+	if (dsos == NULL) {
+		printf("  Memory allocation failed\n");
+		exit(1);
+	}
+
+	if (nftw("/usr/lib/", add_dso, 10, FTW_PHYS) < 0)
+		return;
+
+	pr_debug("  Collected %d DSOs\n", nr_dsos);
+}
+
+static void release_dso(void)
+{
+	int i;
+
+	for (i = 0; i < nr_dsos; i++) {
+		struct bench_dso *dso = &dsos[i];
+
+		free(dso->name);
+	}
+	free(dsos);
+}
+
+/* Fake address used by mmap and sample events */
+static u64 dso_map_addr(struct bench_dso *dso)
+{
+	return 0x400000ULL + dso->ino * 8192ULL;
+}
+
+static u32 synthesize_attr(struct bench_data *data)
+{
+	union perf_event event;
+
+	memset(&event, 0, sizeof(event.attr) + sizeof(u64));
+
+	event.header.type = PERF_RECORD_HEADER_ATTR;
+	event.header.size = sizeof(event.attr) + sizeof(u64);
+
+	event.attr.attr.type = PERF_TYPE_SOFTWARE;
+	event.attr.attr.config = PERF_COUNT_SW_TASK_CLOCK;
+	event.attr.attr.exclude_kernel = 1;
+	event.attr.attr.sample_id_all = 1;
+	event.attr.attr.sample_type = bench_sample_type;
+
+	return writen(data->input_pipe[1], &event, event.header.size);
+}
+
+static u32 synthesize_fork(struct bench_data *data)
+{
+	union perf_event event;
+
+	memset(&event, 0, sizeof(event.fork) + bench_id_hdr_size);
+
+	event.header.type = PERF_RECORD_FORK;
+	event.header.misc = PERF_RECORD_MISC_FORK_EXEC;
+	event.header.size = sizeof(event.fork) + bench_id_hdr_size;
+
+	event.fork.ppid = 1;
+	event.fork.ptid = 1;
+	event.fork.pid = data->pid;
+	event.fork.tid = data->pid;
+
+	return writen(data->input_pipe[1], &event, event.header.size);
+}
+
+static u32 synthesize_mmap(struct bench_data *data, struct bench_dso *dso,
+			   u64 timestamp)
+{
+	union perf_event event;
+	size_t len = offsetof(struct perf_record_mmap2, filename);
+	u64 *id_hdr_ptr = (void *)&event;
+	int ts_idx;
+
+	len += roundup(strlen(dso->name) + 1, 8) + bench_id_hdr_size;
+
+	memset(&event, 0, min(len, sizeof(event.mmap2)));
+
+	event.header.type = PERF_RECORD_MMAP2;
+	event.header.misc = PERF_RECORD_MISC_USER;
+	event.header.size = len;
+
+	event.mmap2.pid = data->pid;
+	event.mmap2.tid = data->pid;
+	event.mmap2.maj = MMAP_DEV_MAJOR;
+	event.mmap2.ino = dso->ino;
+
+	strcpy(event.mmap2.filename, dso->name);
+
+	event.mmap2.start = dso_map_addr(dso);
+	event.mmap2.len = 4096;
+	event.mmap2.prot = PROT_EXEC;
+
+	if (len > sizeof(event.mmap2)) {
+		/* write mmap2 event first */
+		writen(data->input_pipe[1], &event, len - bench_id_hdr_size);
+		/* zero-fill sample id header */
+		memset(id_hdr_ptr, 0, bench_id_hdr_size);
+		/* put timestamp in the right position */
+		ts_idx = (bench_id_hdr_size / sizeof(u64)) - 2;
+		id_hdr_ptr[ts_idx] = timestamp;
+		writen(data->input_pipe[1], id_hdr_ptr, bench_id_hdr_size);
+	} else {
+		ts_idx = (len / sizeof(u64)) - 2;
+		id_hdr_ptr[ts_idx] = timestamp;
+		writen(data->input_pipe[1], &event, len);
+	}
+	return len;
+}
+
+static u32 synthesize_sample(struct bench_data *data, struct bench_dso *dso,
+			     u64 timestamp)
+{
+	union perf_event event;
+	struct perf_sample sample = {
+		.tid = data->pid,
+		.pid = data->pid,
+		.ip = dso_map_addr(dso),
+		.time = timestamp,
+	};
+
+	event.header.type = PERF_RECORD_SAMPLE;
+	event.header.misc = PERF_RECORD_MISC_USER;
+	event.header.size = perf_event__sample_event_size(&sample, bench_sample_type, 0);
+
+	perf_event__synthesize_sample(&event, bench_sample_type, 0, &sample);
+
+	return writen(data->input_pipe[1], &event, event.header.size);
+}
+
+static u32 synthesize_flush(struct bench_data *data)
+{
+	struct perf_event_header header = {
+		.size = sizeof(header),
+		.type = PERF_RECORD_FINISHED_ROUND,
+	};
+
+	return writen(data->input_pipe[1], &header, header.size);
+}
+
+static void *data_reader(void *arg)
+{
+	struct bench_data *data = arg;
+	char buf[8192];
+	int flag;
+	int n;
+
+	flag = fcntl(data->output_pipe[0], F_GETFL);
+	fcntl(data->output_pipe[0], F_SETFL, flag | O_NONBLOCK);
+
+	/* read out data from child */
+	while (true) {
+		n = read(data->output_pipe[0], buf, sizeof(buf));
+		if (n > 0)
+			continue;
+		if (n == 0)
+			break;
+
+		if (errno != EINTR && errno != EAGAIN)
+			break;
+
+		usleep(100);
+	}
+
+	close(data->output_pipe[0]);
+	return NULL;
+}
+
+static int setup_injection(struct bench_data *data)
+{
+	int ready_pipe[2];
+	int dev_null_fd;
+	char buf;
+
+	if (pipe(ready_pipe) < 0)
+		return -1;
+
+	if (pipe(data->input_pipe) < 0)
+		return -1;
+
+	if (pipe(data->output_pipe) < 0)
+		return -1;
+
+	data->pid = fork();
+	if (data->pid < 0)
+		return -1;
+
+	if (data->pid == 0) {
+		const char **inject_argv;
+
+		close(data->input_pipe[1]);
+		close(data->output_pipe[0]);
+		close(ready_pipe[0]);
+
+		dup2(data->input_pipe[0], STDIN_FILENO);
+		close(data->input_pipe[0]);
+		dup2(data->output_pipe[1], STDOUT_FILENO);
+		close(data->output_pipe[1]);
+
+		dev_null_fd = open("/dev/null", O_WRONLY);
+		if (dev_null_fd < 0)
+			exit(1);
+
+		dup2(dev_null_fd, STDERR_FILENO);
+
+		inject_argv = calloc(3, sizeof(*inject_argv));
+		if (inject_argv == NULL)
+			exit(1);
+
+		inject_argv[0] = strdup("inject");
+		inject_argv[1] = strdup("-b");
+
+		/* signal that we're ready to go */
+		close(ready_pipe[1]);
+
+		cmd_inject(2, inject_argv);
+
+		exit(0);
+	}
+
+	pthread_create(&data->th, NULL, data_reader, data);
+
+	close(ready_pipe[1]);
+	close(data->input_pipe[0]);
+	close(data->output_pipe[1]);
+
+	/* wait for child ready */
+	if (read(ready_pipe[0], &buf, 1) < 0)
+		return -1;
+	close(ready_pipe[0]);
+
+	return 0;
+}
+
+static int inject_build_id(struct bench_data *data, u64 *max_rss)
+{
+	int status;
+	unsigned int i, k;
+	struct rusage rusage;
+	u64 len = 0;
+
+	/* this makes the child to run */
+	if (perf_header__write_pipe(data->input_pipe[1]) < 0)
+		return -1;
+
+	len += synthesize_attr(data);
+	len += synthesize_fork(data);
+
+	for (i = 0; i < nr_mmaps; i++) {
+		int idx = rand() % (nr_dsos - 1);
+		struct bench_dso *dso = &dsos[idx];
+		u64 timestamp = rand() % 1000000;
+
+		pr_debug2("   [%d] injecting: %s\n", i+1, dso->name);
+		len += synthesize_mmap(data, dso, timestamp);
+
+		for (k = 0; k < nr_samples; k++)
+			len += synthesize_sample(data, dso, timestamp + k * 1000);
+
+		if ((i + 1) % 10 == 0)
+			len += synthesize_flush(data);
+	}
+
+	/* tihs makes the child to finish */
+	close(data->input_pipe[1]);
+
+	wait4(data->pid, &status, 0, &rusage);
+	*max_rss = rusage.ru_maxrss;
+
+	pr_debug("   Child %d exited with %d\n", data->pid, status);
+
+	return 0;
+}
+
+static int do_inject_loop(struct bench_data *data)
+{
+	unsigned int i;
+	struct stats time_stats, mem_stats;
+	double time_average, time_stddev;
+	double mem_average, mem_stddev;
+
+	srand(time(NULL));
+	init_stats(&time_stats);
+	init_stats(&mem_stats);
+	symbol__init(NULL);
+
+	bench_sample_type  = PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_IP;
+	bench_sample_type |= PERF_SAMPLE_TID | PERF_SAMPLE_TIME;
+	bench_id_hdr_size  = 32;
+
+	collect_dso();
+	if (nr_dsos == 0) {
+		printf("  Cannot collect DSOs for injection\n");
+		return -1;
+	}
+
+	for (i = 0; i < iterations; i++) {
+		struct timeval start, end, diff;
+		u64 runtime_us, max_rss;
+
+		pr_debug("  Iteration #%d\n", i+1);
+
+		if (setup_injection(data) < 0) {
+			printf("  Build-id injection setup failed\n");
+			break;
+		}
+
+		gettimeofday(&start, NULL);
+		if (inject_build_id(data, &max_rss) < 0) {
+			printf("  Build-id injection failed\n");
+			break;
+		}
+
+		gettimeofday(&end, NULL);
+		timersub(&end, &start, &diff);
+		runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+		update_stats(&time_stats, runtime_us);
+		update_stats(&mem_stats, max_rss);
+
+		pthread_join(data->th, NULL);
+	}
+
+	time_average = avg_stats(&time_stats) / USEC_PER_MSEC;
+	time_stddev = stddev_stats(&time_stats) / USEC_PER_MSEC;
+	printf("  Average build-id injection took: %.3f msec (+- %.3f msec)\n",
+		time_average, time_stddev);
+
+	/* each iteration, it processes MMAP2 + BUILD_ID + nr_samples * SAMPLE */
+	time_average = avg_stats(&time_stats) / (nr_mmaps * (nr_samples + 2));
+	time_stddev = stddev_stats(&time_stats) / (nr_mmaps * (nr_samples + 2));
+	printf("  Average time per event: %.3f usec (+- %.3f usec)\n",
+		time_average, time_stddev);
+
+	mem_average = avg_stats(&mem_stats);
+	mem_stddev = stddev_stats(&mem_stats);
+	printf("  Average memory usage: %.0f KB (+- %.0f KB)\n",
+		mem_average, mem_stddev);
+
+	release_dso();
+	return 0;
+}
+
+int bench_inject_build_id(int argc, const char **argv)
+{
+	struct bench_data data;
+
+	argc = parse_options(argc, argv, options, bench_usage, 0);
+	if (argc) {
+		usage_with_options(bench_usage, options);
+		exit(EXIT_FAILURE);
+	}
+
+	return do_inject_loop(&data);
+}
+
diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
index 4f176039fc8f..62a7b7420a44 100644
--- a/tools/perf/builtin-bench.c
+++ b/tools/perf/builtin-bench.c
@@ -87,6 +87,7 @@ static struct bench epoll_benchmarks[] = {
 static struct bench internals_benchmarks[] = {
 	{ "synthesize", "Benchmark perf event synthesis",	bench_synthesize	},
 	{ "kallsyms-parse", "Benchmark kallsyms parsing",	bench_kallsyms_parse	},
+	{ "inject-build-id", "Benchmark build-id injection",	bench_inject_build_id	},
 	{ NULL,		NULL,					NULL			}
 };
 
diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index 6d2f410d773a..e4d78f11494e 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -441,11 +441,10 @@ static int dso__inject_build_id(struct dso *dso, struct perf_tool *tool,
 	return 0;
 }
 
-static int perf_event__inject_buildid(struct perf_tool *tool,
-				      union perf_event *event,
-				      struct perf_sample *sample,
-				      struct evsel *evsel __maybe_unused,
-				      struct machine *machine)
+int perf_event__inject_buildid(struct perf_tool *tool, union perf_event *event,
+			       struct perf_sample *sample,
+			       struct evsel *evsel __maybe_unused,
+			       struct machine *machine)
 {
 	struct addr_location al;
 	struct thread *thread;
diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index aad419bb165c..949f7e54c9cb 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -29,6 +29,10 @@ int build_id__mark_dso_hit(struct perf_tool *tool, union perf_event *event,
 
 int dsos__hit_all(struct perf_session *session);
 
+int perf_event__inject_buildid(struct perf_tool *tool, union perf_event *event,
+			       struct perf_sample *sample, struct evsel *evsel,
+			       struct machine *machine);
+
 bool perf_session__read_build_ids(struct perf_session *session, bool with_hits);
 int perf_session__write_buildid_table(struct perf_session *session,
 				      struct feat_fd *fd);