Derek Xu
2877d78576
This is a reland of commit 22021cc120
I showed some excerpts of Golem results to @mraleph for varying targets
and constant CPU, patch A, and patch B. Those constants being:
CPU: Intel Xeon
patch A: revision=115869&patch=20143
patch B: revision=115876
(example results:
https://golem.corp.goog/Comparison?repository=dart#targetA%3Ddart%3BmachineTypeA%3Dlinux-x64%3BrevisionA%3D115869%3BpatchA%3Dderekx-Reland---VM%2FService--Record-timeline-events-representing-completed-microtasks--4%3BtargetB%3Ddart%3BmachineTypeB%3Dlinux-x64%3BrevisionB%3D115876%3BpatchB%3DNone)
He said that this change could be relanded as long as the following
"RunTime as Score" regressions of the "dart" target were noted in the
commit message:
- StreamSingleSubTest: -3.907% (-0.8 noise)
- ScheduleMicrotaskTest: -12.67% (-0.6 noise)
TEST=pkg/vm_service/test/timeline_events_for_completed_microtasks_test
Original change's description:
> [VM/Service] Record timeline events representing completed microtasks
>
> TEST=pkg/vm_service/test/timeline_events_for_completed_microtasks_test
>
> CoreLibraryReviewExempt: This CL does not include any core library API
> changes, it only modifies the implementation of microtasks (by
> instrumenting them).
> Change-Id: I54d886db9519c73f9e3218a9cc1c46bc9fe9acc3
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420221
> Commit-Queue: Derek Xu <derekx@google.com>
> Reviewed-by: Ben Konyi <bkonyi@google.com>
CoreLibraryReviewExempt: This CL does not include any core library API
changes, it only modifies the implementation of microtasks (by
instrumenting them).
Change-Id: Ia7741a9bb9ab948e8d5fff1cf9abe9915e247d81
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423921
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Derek Xu <derekx@google.com>
Dart Engine
The include/dart_engine.h provides additional functions to embed the Dart VM
and to call Dart functions from kernel and AOT snapshots. It is not intended to
be a full-featured API, and should be used together with dart_api.h.
It is intended for reusing of existing Dart code in non-Dart programs, and allows to use Dart snapshots as shared libraries: the caller can start one or several isolates from Dart snapshots and call Dart functions from it.
Comparing to dart_api.h it brings the following:
- Full initialization of Dart VM, including initializing core libraries.
- Easier handling of isolate messages
- Lock-guarded functions to enter/exit isolates.
See examples in samples/embedder for usages of the API.
Handling isolate messages
In dart_api.h there are two possible ways to handle asynchronous
isolate messages:
Dart_MessageNotifyCallback: Users can pass a callback to get notifications about messages to handle, but handling messages still requires entering an isolate, entering a scope, callingDart_HandleMessage, and then leaving a scope and an isolate.Dart_RunLoop: Users can invoke it on a separate thread, but then they won't be able to enter isolates from other threads.
As an alternative, dart_engine.h provides a simpler function
DartEngine_HandleMessage, which encapsulates isolate and scope management, and
it allows to specify per isolate / default message schedulers, which only need
to schedule an execution DartEngine_HandleMessage with the right isolate.
Users can create their own DartEngine_MessageScheduler struct and pass it to
DartEngine_SetMessageScheduler / DartEngine_SetDefaultMessageScheduler. See
samples/embedder/run_timer_async.cc and samples/embedder/run_timer.cc
examples.
Entering / leaving isolates
Because engine API uses its own message handling, it is important to use
DartEngine_AcquireIsolate / DartEngine_ReleaseIsolate instead of
Dart_EnterIsolate / Dart_ExitIsolate. DartEngine_AcquireIsolate blocks
until an isolate can be entered by trying to obtain an internal lock (which is
released by DartEngine_ReleaseIsolate), while Dart_EnterIsolate crashes if
some other thread has entered the same isolate.