I collected statistics for the sizes and capacities of growable arrays which are promoted to old-space or survive an old-space gc when running dart2js and Fasta. For these applications, the vast majority of arrays stay empty. More than half of the total object size of promoted backing arrays is backing for empty growable arrays.
Furthermore, since the overhead for an array is 3 words (header, type parameters and length), and object sizes are rounded up to an even number of words, we waste one word for all even-sized arrays.
This CL changes the growth strategy so that empty growable arrays are created with a shared, zero-sized array as backing, avoiding the allocation of a backing array if no elements are added. When the array needs to grow, it starts out at 3 and grows to double size plus one each time: 7, 15, 31, ...
A few places in the VM code need to handle these shared, zero-sized arrays specially. In particular, the Array::MakeArray function needs to allocate a new, empty array if its result is to be returned to Dart code.
Benchmarks suggest that the change improves memory usage by a few percent overall and does not significantly affect run time.
BUG=
R=erikcorry@google.com
Review-Url: https://codereview.chromium.org/2949803002 .
Fix observatory tests broken by running dartfmt due to line and column changes.
Temporarily reverted formatting for evaluate_activation_test.dart as dartfmt doesn't yet handle multitests.
BUG=
R=johnmccutchan@google.com
Review-Url: https://codereview.chromium.org/2759973004 .
I've omitted files where the formatter output is significantly uglier
than the original code and I'll send those files in a separate CL
with options for how to make the code look reasonable while still
taking advantage of the formatter.
BUG=
R=johnmccutchan@google.com
Review-Url: https://codereview.chromium.org/2751423005 .
The analyzer has a stricter patch parser than the VM. Patch files
cannot change signatures of patched members. Specifically, they cannot
change:
- the return type
- a parameter's name
- a parameter to an initializing formal
- an optional parameter's default value
BUG=
R=asiva@google.com
Review-Url: https://codereview.chromium.org/2612043002 .
This should help least-upper-bound computations to not think of EfficientLength
as completely separate from Iterable even though they are always used together.
It doesn't solve all problems with the least-upper-bound computation,
but at least some of the more often occuring ones.
R=floitsch@google.com
Review URL: https://codereview.chromium.org/2467113003 .
Allow members of patch classes to be annotated with @patch. The VM
ignores the annotation. I simply replaces the original method
if the name matches, or reports an error if field names match.
Adding a bit is_patched to members to do more checking remains a
TODO. There are currently no unused bits available, and I don’t want
to increase the size of Function objects for this.
BUG=
R=asiva@google.com
Review URL: https://codereview.chromium.org/2230383003 .
Annotate patch classes and top-level patch functions with @patch
instead of the pseudo-keyword patch. This allows the analyzer
to read patch files, and matches the syntax that dart2js uses.
The deprecated syntax is still supported, but a warning is printed when detected.
BUG=
Review URL: https://codereview.chromium.org/2220883004 .
It's still not a good solution for detecting an Iterable with an efficient
length. It's not inherited by, e.g., a DelegatingIterable wrapper or similar
generic Iterable transformers.
Keep this as an internal optimization for quickly detecting the most common
efficient-length Iterable classes (List, Set, Queue, Map.keys/values), but
don't make it public.
A *real* solution would be adding a hasEfficientLength getter to Iterable, or
adding an efficientLength getter that may return null if it's not efficient.
This would something that a wrapper can attach to.
R=sgjesse@google.com
Review URL: https://codereview.chromium.org//1154263003
Peter von der Ahé