From: Eduard Zingerman <eddyz87@gmail.com>
To: Alan Maguire <alan.maguire@oracle.com>,
andrii@kernel.org, jolsa@kernel.org, acme@redhat.com,
quentin@isovalent.com
Cc: mykolal@fb.com, ast@kernel.org, daniel@iogearbox.net,
martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, houtao1@huawei.com, bpf@vger.kernel.org,
masahiroy@kernel.org, mcgrof@kernel.org, nathan@kernel.org
Subject: Re: [PATCH v3 bpf-next 03/11] libbpf: add btf__parse_opts() API for flexible BTF parsing
Date: Mon, 13 May 2024 09:59:14 -0700 [thread overview]
Message-ID: <9ebe310153e4ac0f52ea861a857950686f5f6f77.camel@gmail.com> (raw)
In-Reply-To: <5e2acba0-5860-4e6d-8b5f-bb63bd4d89f8@oracle.com>
On Mon, 2024-05-13 at 17:25 +0100, Alan Maguire wrote:
> On 11/05/2024 10:40, Eduard Zingerman wrote:
> > On Fri, 2024-05-10 at 11:30 +0100, Alan Maguire wrote:
> > > Options cover existing parsing scenarios (ELF, raw, retrieving
> > > .BTF.ext) and also allow specification of the ELF section name
> > > containing BTF. This will allow consumers to retrieve BTF from
> > > .BTF.base sections (BTF_BASE_ELF_SEC) also.
> > >
> > > Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> > > ---
> >
> > For the sake of discussion, what are the benefits of adding
> > btf__parse_opts(), compared to modifying btf__parse() to check if
> > .BTF.base is present and acting accordingly?
> > btf__parse() already does a guess if passed argument is an ELF or a
> > RAW file, so such guessing semantics seems to be a natural extension.
>
> It's a good idea. The only thing I'd say against it is that we already
> have existing semantics there that are well-established, and the
> .BTF.base scenario will be relatively rare, yet the check would I think
> be a tax all .BTF-only cases will have to pay. We'd presumably check
> .BTF.base, and if not present check for .BTF. So all callers of
> btf__parse() when accessing .BTF sections would be checking for
> .BTF.base first.
You are talking about the cost of scanning all sections in the ELF file, right?
It looks like btf.c:btf_parse_elf() already scans all sections once,
maybe this code could be re-organized slightly to parse the base
if .BTF.base section is present?
Does not seem that this would incur a measurable runtime cost.
Or do you have something else in mind?
> In that context, it seemed to make sense to support an explicit request
> for a specific section (via btf__parse_opts()) rather than inducing
> overhead in existing checks. But again, if the overhead isn't seen as an
> issue, we could absolutely do it.
next prev parent reply other threads:[~2024-05-13 16:59 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-10 10:30 [PATCH v3 bpf-next 00/11] bpf: support resilient split BTF Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 01/11] libbpf: add btf__distill_base() creating split BTF with distilled base BTF Alan Maguire
2024-05-10 19:14 ` Eduard Zingerman
2024-05-13 17:23 ` Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 02/11] selftests/bpf: test distilled base, split BTF generation Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 03/11] libbpf: add btf__parse_opts() API for flexible BTF parsing Alan Maguire
2024-05-11 9:40 ` Eduard Zingerman
2024-05-13 16:25 ` Alan Maguire
2024-05-13 16:59 ` Eduard Zingerman [this message]
2024-05-10 10:30 ` [PATCH v3 bpf-next 04/11] bpftool: support displaying raw split BTF using base BTF section as base Alan Maguire
2024-05-13 10:57 ` Quentin Monnet
2024-05-10 10:30 ` [PATCH v3 bpf-next 05/11] resolve_btfids: use .BTF.base ELF section as base BTF if -B option is used Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 06/11] kbuild, bpf: add module-specific pahole/resolve_btfids flags for distilled base BTF Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 07/11] libbpf: split BTF relocation Alan Maguire
2024-05-10 22:26 ` Eduard Zingerman
2024-05-13 17:51 ` Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 08/11] selftests/bpf: extend distilled BTF tests to cover " Alan Maguire
2024-05-10 22:46 ` Eduard Zingerman
2024-05-10 10:30 ` [PATCH v3 bpf-next 09/11] module, bpf: store BTF base pointer in struct module Alan Maguire
2024-05-10 10:30 ` [PATCH v3 bpf-next 10/11] libbpf,bpf: share BTF relocate-related code with kernel Alan Maguire
2024-05-11 1:46 ` Eduard Zingerman
2024-05-14 16:14 ` Alan Maguire
2024-05-15 6:56 ` Eduard Zingerman
2024-05-10 10:30 ` [PATCH v3 bpf-next 11/11] bpftool: support displaying relocated-with-base split BTF Alan Maguire
2024-05-11 9:32 ` Eduard Zingerman
2024-05-13 11:12 ` Quentin Monnet
2024-05-14 16:33 ` Alan Maguire
2024-05-11 9:28 ` [PATCH v3 bpf-next 00/11] bpf: support resilient " Eduard Zingerman
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