From: Blake Jones <blakejones@google.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Chun-Tse Shao <ctshao@google.com>,
Zhongqiu Han <quic_zhonhan@quicinc.com>,
James Clark <james.clark@linaro.org>,
Charlie Jenkins <charlie@rivosinc.com>,
Andi Kleen <ak@linux.intel.com>,
Dmitry Vyukov <dvyukov@google.com>, Leo Yan <leo.yan@arm.com>,
Yujie Liu <yujie.liu@intel.com>,
Graham Woodward <graham.woodward@arm.com>,
Yicong Yang <yangyicong@hisilicon.com>,
Ben Gainey <ben.gainey@arm.com>,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-perf-users@vger.kernel.org
Subject: Re: [PATCH 2/3] perf: collect BPF metadata from existing BPF programs
Date: Tue, 3 Jun 2025 15:29:35 -0700 [thread overview]
Message-ID: <CAP_z_Cg0ZCfvEFpJpvhuRcUkjV_paCODw2J61D3YQMm7dg0aGg@mail.gmail.com> (raw)
In-Reply-To: <aD9yte49C_BM5oA9@google.com>
On Tue, Jun 3, 2025 at 3:10 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > Hmmm. Is that documented and tested anywhere? Offhand it sounds like an
> > implementation detail that I wouldn't feel great about depending on -
> > certainly not without a strong guarantee that it wouldn't change.
>
> Good point. Maybe BPF folks have some idea?
>
> Anyway the current code generates them together in a function.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/events/core.c?h=v6.15#n9825
It certainly does, yeah. But I don't want to have that become another
instance of https://www.hyrumslaw.com/.
> > Can you say more about why the duplicated records concern you?
>
> More data means more chance to lost something. I don't expect this is
> gonna be a practical concern but in general we should pursue less data.
That makes sense. In this case, it will only show up for BPF programs that
define "bpf_metadata_" variables (which is already an opt-in action), and
the number of variables a given program defines is likely to be quite small.
So I think the cost of the marginal increase in data generated is outweighed
by the usability and reliability benefits of being able to match these events
1:1 with the KSYMBOL events. If this proves to be a problem in practice,
it can be revisited.
Blake
next prev parent reply other threads:[~2025-06-03 22:29 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-21 22:27 [PATCH 0/3] perf: generate events for BPF metadata Blake Jones
2025-05-21 22:27 ` [PATCH 1/3] perf: add support for printing BTF character arrays as strings Blake Jones
2025-05-22 17:42 ` Arnaldo Carvalho de Melo
2025-05-22 18:19 ` Blake Jones
2025-05-29 0:58 ` Blake Jones
2025-05-30 17:40 ` Namhyung Kim
2025-05-31 7:26 ` Blake Jones
2025-06-03 18:23 ` Blake Jones
2025-06-03 18:43 ` Alexei Starovoitov
2025-06-03 19:47 ` Namhyung Kim
2025-05-21 22:27 ` [PATCH 2/3] perf: collect BPF metadata from existing BPF programs Blake Jones
2025-05-29 17:47 ` Ian Rogers
2025-05-29 23:21 ` Blake Jones
2025-05-29 23:23 ` Ian Rogers
2025-06-03 20:15 ` Namhyung Kim
2025-06-03 21:27 ` Blake Jones
2025-06-03 21:44 ` Namhyung Kim
2025-06-03 21:54 ` Blake Jones
2025-06-03 22:09 ` Namhyung Kim
2025-06-03 22:29 ` Blake Jones [this message]
2025-06-04 21:40 ` Namhyung Kim
2025-06-04 22:12 ` Arnaldo Carvalho de Melo
2025-06-04 23:04 ` Blake Jones
2025-05-21 22:27 ` [PATCH 3/3] perf: collect BPF metadata from new programs, and display the new event Blake Jones
2025-05-29 18:12 ` Ian Rogers
2025-05-29 23:09 ` Blake Jones
2025-05-29 23:27 ` Ian Rogers
2025-05-29 23:49 ` Blake Jones
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