[tracing] Enable system-backend startup tracing in trace_startup [chromium/src : main]

[Clemens Backes (Gerrit)]

Attention needed from Mikhail Khokhlov

Clemens Backes added 2 comments

Patchset-level comments

File-level comment, Patchset 1 (Latest):

Clemens Backes . resolved

PTAL. Gemini claims that this fixes the remaining timing gap on the linked issue.

File services/tracing/public/cpp/trace_startup.cc

Line 150, Patchset 1 (Latest): // TODO(khokhlov): Support startup tracing with the system backend in the
// SDK build.

Clemens Backes . unresolved

Is this change already enough to resolve this TODO?

Open in Gerrit

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• Mikhail Khokhlov

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Gerrit-Change-Number: 8116953

Gerrit-PatchSet: 1

Gerrit-Owner: Clemens Backes <clem...@chromium.org>

Gerrit-Reviewer: Clemens Backes <clem...@chromium.org>

Gerrit-Reviewer: Mikhail Khokhlov <khok...@google.com>

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Gerrit-Comment-Date: Mon, 20 Jul 2026 12:17:10 +0000

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[Mikhail Khokhlov (Gerrit)]

Attention needed from Clemens Backes

Mikhail Khokhlov added 1 comment

File services/tracing/public/cpp/trace_startup.cc

Line 150, Patchset 1 (Latest): // TODO(khokhlov): Support startup tracing with the system backend in the
// SDK build.

Clemens Backes . unresolved

Is this change already enough to resolve this TODO?

Mikhail Khokhlov

My memory of this code is weak, but I'm pretty sure that it's not that simple. The backend has to adopt the pre-allocated shared memory buffer, which the system backend does not know how to do.

CC etiennep@ who has better understanding of this system.

Open in Gerrit

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Attention is currently required from:

• Clemens Backes

Submit Requirements:

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• Code-Owners
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Gerrit-Project: chromium/src

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Gerrit-Change-Id: Ibc20640cc2f74c5d5753c88b676147183cd5f2cb

Gerrit-Change-Number: 8116953

Gerrit-PatchSet: 1

Gerrit-Owner: Clemens Backes <clem...@chromium.org>

Gerrit-Reviewer: Clemens Backes <clem...@chromium.org>

Gerrit-Reviewer: Mikhail Khokhlov <khok...@google.com>

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Gerrit-Comment-Date: Mon, 20 Jul 2026 14:02:43 +0000

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Comment-In-Reply-To: Clemens Backes <clem...@chromium.org>

[Etienne Pierre-Doray (Gerrit)]

Attention needed from Clemens Backes

Etienne Pierre-Doray added 2 comments

File services/tracing/public/cpp/trace_startup.cc

Line 146, Patchset 1 (Latest): auto perfetto_config = startup_config.GetPerfettoConfig();

Etienne Pierre-Doray . unresolved

If starting tracing through perfetto directly, I don't think chrome forwards it the config to renderer (unlike passing config through chrome's command line).
For startup tracing in child processes to work for system backend, we'd need the browser to forward any active config; TraceStartupConfig currently does this only for the config given in command line.

Line 150, Patchset 1 (Latest): // TODO(khokhlov): Support startup tracing with the system backend in the
// SDK build.

Clemens Backes . unresolved

Is this change already enough to resolve this TODO?

Mikhail Khokhlov

My memory of this code is weak, but I'm pretty sure that it's not that simple. The backend has to adopt the pre-allocated shared memory buffer, which the system backend does not know how to do.

CC etiennep@ who has better understanding of this system.

Etienne Pierre-Doray

+1 the system backend would need to know how to adopt buffers, passed through ConnectProducerArgs.

Gerrit-Comment-Date: Mon, 27 Jul 2026 20:03:35 +0000

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Comment-In-Reply-To: Mikhail Khokhlov <khok...@google.com>

Comment-In-Reply-To: Clemens Backes <clem...@chromium.org>

[Etienne Pierre-Doray (Gerrit)]

Attention needed from Clemens Backes

Etienne Pierre-Doray added 1 comment

File services/tracing/public/cpp/trace_startup.cc

Line 146, Patchset 1 (Latest): auto perfetto_config = startup_config.GetPerfettoConfig();

Etienne Pierre-Doray . unresolved

If starting tracing through perfetto directly, I don't think chrome forwards it the config to renderer (unlike passing config through chrome's command line).
For startup tracing in child processes to work for system backend, we'd need the browser to forward any active config; TraceStartupConfig currently does this only for the config given in command line.

Etienne Pierre-Doray

We also don't currently forward the full config, only track_event one.

Gerrit-Comment-Date: Mon, 27 Jul 2026 20:23:41 +0000

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Comment-In-Reply-To: Etienne Pierre-Doray <etie...@chromium.org>