Re: [PATCH bpf-next 5/5] selftests/bpf: add benchmark for uprobe vs. user_prog

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Song Liu <songliubraving@fb.com>
Cc: open list <linux-kernel@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>,
	john fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Daniel Xu <dlxu@fb.com>
Subject: Re: [PATCH bpf-next 5/5] selftests/bpf: add benchmark for uprobe vs. user_prog
Date: Sun, 2 Aug 2020 18:51:32 -0700	[thread overview]
Message-ID: <CAEf4BzaP4TGF7kcmZRAKsy=oWPpFA6sUGFkctpGz-fPp+YuSOQ@mail.gmail.com> (raw)
In-Reply-To: <20200801084721.1812607-6-songliubraving@fb.com>

On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@fb.com> wrote:
>
> Add a benchmark to compare performance of
>   1) uprobe;
>   2) user program w/o args;
>   3) user program w/ args;
>   4) user program w/ args on random cpu.
>

Can you please add it to the existing benchmark runner instead, e.g.,
along the other bench_trigger benchmarks? No need to re-implement
benchmark setup. And also that would also allow to compare existing
ways of cheaply triggering a program vs this new _USER program?

If the performance is not significantly better than other ways, do you
think it still makes sense to add a new BPF program type? I think
triggering KPROBE/TRACEPOINT from bpf_prog_test_run() would be very
nice, maybe it's possible to add that instead of a new program type?
Either way, let's see comparison with other program triggering
mechanisms first.

> Sample output:
>
> ./test_progs -t uprobe_vs_user_prog -v
> test_uprobe_vs_user_prog:PASS:uprobe_vs_user_prog__open_and_load 0 nsec
> test_uprobe_vs_user_prog:PASS:get_base_addr 0 nsec
> test_uprobe_vs_user_prog:PASS:attach_uprobe 0 nsec
> run_perf_test:PASS:uprobe 0 nsec
> Each uprobe uses 1419 nanoseconds
> run_perf_test:PASS:user_prog_no_args 0 nsec
> Each user_prog_no_args uses 313 nanoseconds
> run_perf_test:PASS:user_prog_with_args 0 nsec
> Each user_prog_with_args uses 335 nanoseconds
> run_perf_test:PASS:user_prog_with_args_on_cpu 0 nsec
> Each user_prog_with_args_on_cpu uses 2821 nanoseconds
> Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
>
> Signed-off-by: Song Liu <songliubraving@fb.com>
> ---
>  .../bpf/prog_tests/uprobe_vs_user_prog.c      | 101 ++++++++++++++++++
>  .../selftests/bpf/progs/uprobe_vs_user_prog.c |  21 ++++
>  2 files changed, 122 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/uprobe_vs_user_prog.c
>  create mode 100644 tools/testing/selftests/bpf/progs/uprobe_vs_user_prog.c
>

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