Re: [PATCH v3 bpf-next 3/4] selftests/bpf: measure bpf_loop verifier performance

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Mon, Nov 29, 2021 at 2:39 PM Joanne Koong <joannekoong@fb.com> wrote:
>
> This patch tests bpf_loop in pyperf and strobemeta, and measures the
> verifier performance of replacing the traditional for loop
> with bpf_loop.
>
> The results are as follows:
>
> ~strobemeta~
>
> Baseline
>     verification time 6808200 usec
>     stack depth 496
>     processed 554252 insns (limit 1000000) max_states_per_insn 16
>     total_states 15878 peak_states 13489  mark_read 3110
>     #192 verif_scale_strobemeta:OK (unrolled loop)
>
> Using bpf_loop
>     verification time 31589 usec
>     stack depth 96+400
>     processed 1513 insns (limit 1000000) max_states_per_insn 2
>     total_states 106 peak_states 106 mark_read 60
>     #193 verif_scale_strobemeta_bpf_loop:OK
>
> ~pyperf600~
>
> Baseline
>     verification time 29702486 usec
>     stack depth 368
>     processed 626838 insns (limit 1000000) max_states_per_insn 7
>     total_states 30368 peak_states 30279 mark_read 748
>     #182 verif_scale_pyperf600:OK (unrolled loop)
>
> Using bpf_loop
>     verification time 148488 usec
>     stack depth 320+40
>     processed 10518 insns (limit 1000000) max_states_per_insn 10
>     total_states 705 peak_states 517 mark_read 38
>     #183 verif_scale_pyperf600_bpf_loop:OK
>
> Using the bpf_loop helper led to approximately a 99% decrease
> in the verification time and in the number of instructions.
>
> Signed-off-by: Joanne Koong <joannekoong@fb.com>
> ---

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  .../bpf/prog_tests/bpf_verif_scale.c          | 12 +++
>  tools/testing/selftests/bpf/progs/pyperf.h    | 71 +++++++++++++++++-
>  .../selftests/bpf/progs/pyperf600_bpf_loop.c  |  6 ++
>  .../testing/selftests/bpf/progs/strobemeta.h  | 75 ++++++++++++++++++-
>  .../selftests/bpf/progs/strobemeta_bpf_loop.c |  9 +++
>  5 files changed, 169 insertions(+), 4 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/pyperf600_bpf_loop.c
>  create mode 100644 tools/testing/selftests/bpf/progs/strobemeta_bpf_loop.c
>

[...]

>                 /* Unwind python stack */
>                 for (int i = 0; i < STACK_MAX_LEN; ++i) {
>                         if (frame_ptr && get_frame_data(frame_ptr, pidData, &frame, &sym)) {
> @@ -251,6 +319,7 @@ int __on_event(struct bpf_raw_tracepoint_args *ctx)
>                                 frame_ptr = frame.f_back;
>                         }
>                 }
> +#endif /* USE_BPF_LOOP */
>                 event->stack_complete = frame_ptr == NULL;
>         } else {
>                 event->stack_complete = 1;
> diff --git a/tools/testing/selftests/bpf/progs/pyperf600_bpf_loop.c b/tools/testing/selftests/bpf/progs/pyperf600_bpf_loop.c
> new file mode 100644
> index 000000000000..bde8baed4ca6
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/pyperf600_bpf_loop.c
> @@ -0,0 +1,6 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2021 Facebook

nit: should be /* ... */

> +
> +#define STACK_MAX_LEN 600
> +#define USE_BPF_LOOP
> +#include "pyperf.h"

[...]

> diff --git a/tools/testing/selftests/bpf/progs/strobemeta_bpf_loop.c b/tools/testing/selftests/bpf/progs/strobemeta_bpf_loop.c
> new file mode 100644
> index 000000000000..e6f9f920e68a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/strobemeta_bpf_loop.c
> @@ -0,0 +1,9 @@
> +// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> +// Copyright (c) 2021 Facebook

same

> +
> +#define STROBE_MAX_INTS 2
> +#define STROBE_MAX_STRS 25
> +#define STROBE_MAX_MAPS 100
> +#define STROBE_MAX_MAP_ENTRIES 20
> +#define USE_BPF_LOOP
> +#include "strobemeta.h"
> --
> 2.30.2
>