From: Quentin Monnet <qmo@kernel.org>
To: chenyuan_fl@163.com, bpf@vger.kernel.org
Cc: Yuan Chen <chenyuan@kylinos.cn>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next] bpftool: Print map_extra in map show
Date: Fri, 16 Oct 2026 15:25:06 +0100 [thread overview]
Message-ID: <b0cd17c2-2c57-4663-848e-f5831b275124@kernel.org> (raw)
In-Reply-To: <20261016071700.280539-2-chenyuan_fl@163.com>
2026-10-16 15:16 UTC+0800 ~ chenyuan_fl@163.com
> From: Yuan Chen <chenyuan@kylinos.cn>
>
> bpf_map_info::map_extra carries per-map-type creation attributes
> (hash function count for bloom filter, VMA start for arena). The
> kernel prints it in fdinfo, but bpftool does not. Print the raw
> value in plain and JSON output when non-zero, without interpreting
> it per map type, like map_flags. The attribute is already overloaded
> per map type, and bpftool must not grow per-type knowledge of it.
Why not? Do we expect the semantic of map_extra to change? Having
something like "nr_hash_funcs 7" in plain output in the case of a Bloom
filter would be easier to interpret?
>
> Example (bloom filter with 7 hash functions):
>
> 117665: bloom_filter name featu_bloom flags 0x0
> key 0B value 8B max_entries 128 map_extra 0x7 memlock 520B
> pids fixture(3543054)
>
> Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
next prev parent reply other threads:[~2026-10-16 14:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-16 7:16 [PATCH bpf-next] bpftool: Print verified instruction count in prog show chenyuan_fl
2026-10-16 7:16 ` [PATCH bpf-next] bpftool: Print map_extra in map show chenyuan_fl
2026-10-16 14:25 ` Quentin Monnet [this message]
2026-10-16 14:13 ` [PATCH bpf-next] bpftool: Print verified instruction count in prog show Justin Suess
2026-10-16 14:24 ` Quentin Monnet
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