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tools: bpftool: use PERF_SAMPLE_TIME instead of reading the clock 

Ask the kernel to include sample time in each even instead of
reading the clock.  This is also more accurate because our
clock reading was done when user space would dump the buffer,
not when sample was produced.

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Jakub Kicinski 2018-05-10 10:24:37 -07:00 committed by Daniel Borkmann
parent cb9c28ef57
commit e3687510fc
1 changed files with 6 additions and 11 deletions
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17
tools/bpf/bpftool/map_perf_ring.c
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@ -39,6 +39,7 @@ struct event_ring_info {
struct perf_event_sample { struct perf_event_sample {
struct perf_event_header header; struct perf_event_header header;
u64 time;
__u32 size; __u32 size;
unsigned char data[]; unsigned char data[];
}; };
@ -57,17 +58,9 @@ print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
__u64 id; __u64 id;
__u64 lost; __u64 lost;
} *lost = (void *)e; } *lost = (void *)e;
struct timespec ts;
if (clock_gettime(CLOCK_MONOTONIC, &ts)) {
perror("Can't read clock for timestamp");
return;
}
if (json_output) { if (json_output) {
jsonw_start_object(json_wtr); jsonw_start_object(json_wtr);
jsonw_name(json_wtr, "timestamp");
jsonw_uint(json_wtr, ts.tv_sec * 1000000000ull + ts.tv_nsec);
jsonw_name(json_wtr, "type"); jsonw_name(json_wtr, "type");
jsonw_uint(json_wtr, e->header.type); jsonw_uint(json_wtr, e->header.type);
jsonw_name(json_wtr, "cpu"); jsonw_name(json_wtr, "cpu");
@ -75,6 +68,8 @@ print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
jsonw_name(json_wtr, "index"); jsonw_name(json_wtr, "index");
jsonw_uint(json_wtr, ring->key); jsonw_uint(json_wtr, ring->key);
if (e->header.type == PERF_RECORD_SAMPLE) { if (e->header.type == PERF_RECORD_SAMPLE) {
jsonw_name(json_wtr, "timestamp");
jsonw_uint(json_wtr, e->time);
jsonw_name(json_wtr, "data"); jsonw_name(json_wtr, "data");
print_data_json(e->data, e->size); print_data_json(e->data, e->size);
} else if (e->header.type == PERF_RECORD_LOST) { } else if (e->header.type == PERF_RECORD_LOST) {
@ -89,8 +84,8 @@ print_bpf_output(struct event_ring_info *ring, struct perf_event_sample *e)
jsonw_end_object(json_wtr); jsonw_end_object(json_wtr);
} else { } else {
if (e->header.type == PERF_RECORD_SAMPLE) { if (e->header.type == PERF_RECORD_SAMPLE) {
printf("== @%ld.%ld CPU: %d index: %d =====\n", printf("== @%lld.%09lld CPU: %d index: %d =====\n",
(long)ts.tv_sec, ts.tv_nsec, e->time / 1000000000ULL, e->time % 1000000000ULL,
ring->cpu, ring->key); ring->cpu, ring->key);
fprint_hex(stdout, e->data, e->size, " "); fprint_hex(stdout, e->data, e->size, " ");
printf("\n"); printf("\n");
@ -185,7 +180,7 @@ static void perf_event_unmap(void *mem)
static int bpf_perf_event_open(int map_fd, int key, int cpu) static int bpf_perf_event_open(int map_fd, int key, int cpu)
{ {
struct perf_event_attr attr = { struct perf_event_attr attr = {
.sample_type = PERF_SAMPLE_RAW, .sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_TIME,
.type = PERF_TYPE_SOFTWARE, .type = PERF_TYPE_SOFTWARE,
.config = PERF_COUNT_SW_BPF_OUTPUT, .config = PERF_COUNT_SW_BPF_OUTPUT,
}; };