From: Jiri Olsa <olsajiri@gmail.com>
To: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
andrii@kernel.org, kernel-team@meta.com
Subject: Re: [PATCH bpf-next] selftests/bpf: Use PERF_COUNT_HW_CPU_CYCLES event for get_branch_snapshot
Date: Fri, 7 Apr 2023 21:31:11 +0100 [thread overview]
Message-ID: <ZDB9j2G4pTtNDCJc@krava> (raw)
In-Reply-To: <20230407190130.2093736-1-song@kernel.org>
On Fri, Apr 07, 2023 at 12:01:30PM -0700, Song Liu wrote:
> perf_event with type=PERF_TYPE_RAW and config=0x1b00 turned out to be not
> reliable in ensuring LBR is active. Thus, test_progs:get_branch_snapshot is
> not reliable in some systems. Replace it with PERF_COUNT_HW_CPU_CYCLES
> event, which gives more consistent results.
>
> Signed-off-by: Song Liu <song@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
jirka
> ---
> tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> index 3948da12a528..0394a1156d99 100644
> --- a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
> @@ -37,8 +37,8 @@ static int create_perf_events(void)
>
> /* create perf event */
> attr.size = sizeof(attr);
> - attr.type = PERF_TYPE_RAW;
> - attr.config = 0x1b00;
> + attr.type = PERF_TYPE_HARDWARE;
> + attr.config = PERF_COUNT_HW_CPU_CYCLES;
> attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
> attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL |
> PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
> --
> 2.34.1
>
next prev parent reply other threads:[~2023-04-07 20:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-07 19:01 [PATCH bpf-next] selftests/bpf: Use PERF_COUNT_HW_CPU_CYCLES event for get_branch_snapshot Song Liu
2023-04-07 20:31 ` Jiri Olsa [this message]
2023-04-07 22:30 ` patchwork-bot+netdevbpf
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