Re: [PATCH bpf-next 6/6] selftests/bpf: add test to measure performance of BPF_MAP_DUMP

[Song Liu]

On Wed, Jul 24, 2019 at 10:10 AM Brian Vazquez <brianvv@xxxxxxxxxx> wrote:
>
> This tests compares the amount of time that takes to read an entire
> table of 100K elements on a bpf hashmap using both BPF_MAP_DUMP and
> BPF_MAP_GET_NEXT_KEY + BPF_MAP_LOOKUP_ELEM.
>
> Signed-off-by: Brian Vazquez <brianvv@xxxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/test_maps.c | 65 +++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
> index f7ab401399d40..c4593a8904ca6 100644
> --- a/tools/testing/selftests/bpf/test_maps.c
> +++ b/tools/testing/selftests/bpf/test_maps.c
> @@ -18,6 +18,7 @@
>  #include <sys/socket.h>
>  #include <netinet/in.h>
>  #include <linux/bpf.h>
> +#include <linux/time64.h>
>
>  #include <bpf/bpf.h>
>  #include <bpf/libbpf.h>
> @@ -389,6 +390,69 @@ static void test_hashmap_dump(void)
>         close(fd);
>  }
>
> +static void test_hashmap_dump_perf(void)
> +{
> +       int fd, i, max_entries = 100000;
> +       uint64_t key, value, next_key;
> +       bool next_key_valid = true;
> +       void *buf;
> +       u32 buf_len, entries;
> +       int j = 0;
> +       int clk_id = CLOCK_MONOTONIC;
> +       struct timespec begin, end;
> +       long long time_spent, dump_time_spent;
> +       double res;
> +       int tests[] = {1, 2, 230, 5000, 73000, 100000, 234567};
> +       int test_len = ARRAY_SIZE(tests);
> +       const int elem_size = sizeof(key) + sizeof(value);
> +
> +       fd = helper_fill_hashmap(max_entries);
> +       // Alloc memory considering the largest buffer
> +       buf = malloc(elem_size * tests[test_len-1]);
> +       assert(buf != NULL);
> +
> +test:
> +       entries = tests[j];
> +       buf_len = elem_size*tests[j];
> +       j++;
> +       clock_gettime(clk_id, &begin);
> +       errno = 0;
> +       i = 0;
> +       while (errno == 0) {
> +               bpf_map_dump(fd, !i ? NULL : &key,
> +                                 buf, &buf_len);
> +               if (errno)
> +                       break;
> +               if (!i)
> +                       key = *((uint64_t *)(buf + buf_len - elem_size));
> +               i += buf_len / elem_size;
> +       }
> +       clock_gettime(clk_id, &end);
> +       assert(i  == max_entries);
> +       dump_time_spent = NSEC_PER_SEC * (end.tv_sec - begin.tv_sec) +
> +                         end.tv_nsec - begin.tv_nsec;
> +       next_key_valid = true;
> +       clock_gettime(clk_id, &begin);
> +       assert(bpf_map_get_next_key(fd, NULL, &key) == 0);
> +       for (i = 0; next_key_valid; i++) {
> +               next_key_valid = bpf_map_get_next_key(fd, &key, &next_key) == 0;
> +               assert(bpf_map_lookup_elem(fd, &key, &value) == 0);
> +               key = next_key;
> +       }
> +       clock_gettime(clk_id, &end);
> +       time_spent = NSEC_PER_SEC * (end.tv_sec - begin.tv_sec) +
> +                    end.tv_nsec - begin.tv_nsec;
> +       res = (1-((double)dump_time_spent/time_spent))*100;
> +       printf("buf_len_%u:\t %llu entry-by-entry: %llu improvement %lf\n",
> +              entries, dump_time_spent, time_spent, res);
> +       assert(i  == max_entries);
              ^ extra space after i.

> +
> +       if (j < test_len)
> +               goto test;
> +       free(buf);
> +       close(fd);
> +}
> +
>  static void test_hashmap_zero_seed(void)
>  {
>         int i, first, second, old_flags;
> @@ -1758,6 +1822,7 @@ static void run_all_tests(void)
>         test_hashmap_walk(0, NULL);
>         test_hashmap_zero_seed();
>         test_hashmap_dump();
> +       test_hashmap_dump_perf();
>
>         test_arraymap(0, NULL);
>         test_arraymap_percpu(0, NULL);
> --
> 2.22.0.657.g960e92d24f-goog
>