From: Song Liu <songliubraving@fb.com>
To: Andrii Nakryiko <andriin@fb.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Alexei Starovoitov <ast@fb.com>,
"daniel@iogearbox.net" <daniel@iogearbox.net>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 2/3] libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs
Date: Wed, 26 Jun 2019 18:57:49 +0000 [thread overview]
Message-ID: <3E535E64-3FD8-4B3D-BBBB-033057084319@fb.com> (raw)
In-Reply-To: <20190626061235.602633-3-andriin@fb.com>
> On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of
> possible CPUs. This is impossible to specify at compilation time. This
> change adds automatic setting of PERF_EVENT_ARRAY size to number of
> system CPUs, unless non-zero size is specified explicitly. This allows
> to adjust size for advanced specific cases, while providing convenient
> and logical defaults.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index c74cc535902a..8f2b8a081ba7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2114,6 +2114,7 @@ static int
> bpf_object__create_maps(struct bpf_object *obj)
> {
> struct bpf_create_map_attr create_attr = {};
> + int nr_cpus = 0;
> unsigned int i;
> int err;
>
> @@ -2136,7 +2137,21 @@ bpf_object__create_maps(struct bpf_object *obj)
> create_attr.map_flags = def->map_flags;
> create_attr.key_size = def->key_size;
> create_attr.value_size = def->value_size;
> - create_attr.max_entries = def->max_entries;
> + if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY &&
> + !def->max_entries) {
> + if (!nr_cpus)
> + nr_cpus = libbpf_num_possible_cpus();
> + if (nr_cpus < 0) {
> + pr_warning("failed to determine number of system CPUs: %d\n",
> + nr_cpus);
> + return nr_cpus;
I think we need to goto err_out here.
Thanks,
Song
next prev parent reply other threads:[~2019-06-26 18:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-26 6:12 [PATCH v2 bpf-next 0/3] libbpf: add perf buffer abstraction and API Andrii Nakryiko
2019-06-26 6:12 ` [PATCH v2 bpf-next 1/3] libbpf: add perf buffer API Andrii Nakryiko
2019-06-26 19:02 ` Song Liu
2019-06-27 21:04 ` Daniel Borkmann
2019-06-27 21:45 ` Andrii Nakryiko
2019-06-29 5:56 ` Andrii Nakryiko
2019-06-26 6:12 ` [PATCH v2 bpf-next 2/3] libbpf: auto-set PERF_EVENT_ARRAY size to number of CPUs Andrii Nakryiko
2019-06-26 18:57 ` Song Liu [this message]
2019-06-26 22:31 ` Andrii Nakryiko
2019-06-26 6:12 ` [PATCH v2 bpf-next 3/3] selftests/bpf: test perf buffer API Andrii Nakryiko
2019-06-26 11:55 ` [PATCH v2 bpf-next 0/3] libbpf: add perf buffer abstraction and API Toke Høiland-Jørgensen
2019-06-26 18:41 ` Andrii Nakryiko
2019-06-26 20:50 ` Toke Høiland-Jørgensen
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