Chromium change:
https://chromium.googlesource.com/chromium/src/+/d60aaeea8014c75e2ac421c244b51d38dbef197e
commit d60aaeea8014c75e2ac421c244b51d38dbef197e
Author: Colin Blundell <blundell@chromium.org>
Date: Mon Jun 20 11:01:53 2022 +0000
[Preconnect] Stop specially prioritizing preconnect tasks
This CL eliminates the execution of preconnect tasks on a custom
high-priority task queue that was introduced in
https://chromium-review.googlesource.com/c/chromium/src/+/1527536,
reverting back to the behavior prior to that CL of executing these tasks
on the default (priority-based) task queues. We have done
experimentation and found that execution on the custom high-priority
task queue brought no performance benefits over execution on the default
priority-based task queues (summary in
https://bugs.chromium.org/p/chromium/issues/detail?id=1257582#c28).
Specifically, this CL is implementing the launch of the NoStandaloneQ
arm of the experiment analyzed on that bug. The logic for why this is
the case bears explicit mention:
- NoStandaloneQ enables the "kTreatPreconnectTaskTypeAsDefault"
base::Feature.
- When this feature is enabled, invoking
GetUIThreadTaskRunner({BrowserTaskType::kPreconnect}) returns the
task runner for the task priority of the BrowserTaskTraits instance
created via {BrowserTaskType::kPreconnect}. This task priority is
USER_BLOCKING, since BrowserTaskTraits inherits the default value
from TaskTraits and doesn't modify that default value.
- In this CL, we simply stop passing a TaskRunner to the calls to
BindNewPipeAndPassRemote() made in the preconnect code. When no
TaskRunner is explicitly specified to these calls, they use
SequencedTaskRunnerHandle::Get(). The task runner returned by
SequencedTaskRunnerHandle::Get() on the UI thread (on which these
calls are executing) is also the task runner for the USER_BLOCKING
priority, i.e., the same task runner that is currently being passed
when kTreatPreconnectTaskTypeAsDefault is enabled.
This CL also eliminates the kPreconnect browser task trait, as there
are now no uses of it in the codebase.
Bug: 1257582
Claudio DeSouza
da35f85d8c