TL;DR: This CL is shown to reduce memory usage by ~660MB when asking
for many completions.
Before this CL the analyzer cached `_ElementCompletionData` for every
element that have ever had it calculated. This itself contains new
strings, lists etc.
This was likely (although I'm guessing) done because it was asked for
it a lot: In my benchmarks, asking for at most 250 completions for each
of the first 200 files (twice) it was asked more than 113 million times.
Likely (extrapolating) it would take ~26 minutes creating these if not
cached.
In practise we don't need to ask for >113 million of them though.
Each request only wants at most, say, 100 results and likely fewer.
In the benchmark the `build` command was only run ~31% more times than
the number of caches. Building 100 results (again just using the
average) would take ~1.4 ms so hardly matters.
This CL removes the caching (including the field on many `Element`s),
and only calculates it when needed (i.e. on `build` as it's about to be
sent to the users IDE).
When asking for at most 250 completions in the first 1000 files in flutter/flutter (80+ contexts) we save ~669MB of heap usage, making
the heap usage decrease from ~8.34GB to ~7.69GB.
Details:
```
ExtensionElementImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-1185728.00 +/- 413.05
-8.36% +/- 0.00%
SimpleIdentifierImpl (package:analyzer/src/dart/ast/ast.dart) (bytes):
Difference at 95.0% confidence
-1187104.00 +/- 133935.98
-1.14% +/- 0.13%
_List (dart:core) (instances):
Difference at 95.0% confidence
-1204916.00 +/- 5571.96
-10.08% +/- 0.05%
ConstTopLevelVariableElementImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-1301800.00 +/- 12081.85
-7.93% +/- 0.07%
_OneByteString (dart:core) (instances):
Difference at 95.0% confidence
-1825992.50 +/- 186205.44
-28.49% +/- 2.91%
ConstructorElementImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-5518400.00 +/- 135361.21
-6.29% +/- 0.15%
ClassElementImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-6820704.00 +/- 21606.00
-6.34% +/- 0.02%
CompletionDefaultArgumentList (package:analysis_server/src/services/completion/dart/utilities.dart) (bytes):
Difference at 95.0% confidence
-9054304.00 +/- 6195.82
-100.00% +/- 0.07%
InterfaceTypeImpl (package:analyzer/src/dart/element/type.dart) (bytes):
Difference at 95.0% confidence
-9941600.00 +/- 776821.86
-2.32% +/- 0.18%
ElementLocationImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-10401472.00 +/- 111022.97
-46.19% +/- 0.49%
_TwoByteString (dart:core) (bytes):
Difference at 95.0% confidence
-11262480.00 +/- 227076.11
-11.77% +/- 0.24%
MethodElementImpl (package:analyzer/src/dart/element/element.dart) (bytes):
Difference at 95.0% confidence
-13877752.00 +/- 351565.94
-7.70% +/- 0.20%
_ElementDocumentation (package:analysis_server/src/services/completion/dart/suggestion_builder.dart) (bytes):
Difference at 95.0% confidence
-18954304.00 +/- 202259.10
-100.00% +/- 1.07%
_GrowableList (dart:core) (bytes):
Difference at 95.0% confidence
-23003968.00 +/- 3135.17
-25.12% +/- 0.00%
Location (package:analyzer_plugin/protocol/protocol_common.dart) (bytes):
Difference at 95.0% confidence
-63403200.00 +/- 444171.45
-99.68% +/- 0.70%
_List (dart:core) (bytes):
Difference at 95.0% confidence
-71587648.00 +/- 2062003.75
-5.54% +/- 0.16%
Element (package:analyzer_plugin/protocol/protocol_common.dart) (bytes):
Difference at 95.0% confidence
-79254080.00 +/- 555214.31
-100.00% +/- 0.70%
_ElementCompletionData (package:analysis_server/src/services/completion/dart/suggestion_builder.dart) (bytes):
Difference at 95.0% confidence
-110955712.00 +/- 777300.03
-100.00% +/- 0.70%
_OneByteString (dart:core) (bytes):
Difference at 95.0% confidence
-258932360.00 +/- 9586397.08
-35.00% +/- 1.30%
maxRSS:
Difference at 95.0% confidence
-327434240.00 +/- 121326188.82
-3.05% +/- 1.13%
currentRSS:
Difference at 95.0% confidence
-551153664.00 +/- 121286389.20
-5.34% +/- 1.18%
heapCapacity:
Difference at 95.0% confidence
-555710464.00 +/- 164879781.95
-5.75% +/- 1.71%
heapUsage:
Difference at 95.0% confidence
-701868280.00 +/- 8054728.47
-7.84% +/- 0.09%
```
Change-Id: I3b3631520d56ab36dabaee913e802aa1b7ebacfe
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/326822
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>
Jens Johansen
807d1cf47b