9ffd1677f1
When setting up the initial map for a (class or function) constructor,
we always over-allocate a bunch of in-object properties, in case not
all property assignments happen as `this.prop = val` assignments in
the constructor. However this over-allocation was a bit too aggressive
and added a slack of 8 to each class constructor (plus a minimum of
two, when there was no `this.prop = val` assignment). So in total this
would yield an object with initially 40 in-object property slots in
case of a simple class hierarchy like this:
```js
class A {};
class B extends A {};
class C extends B {};
class D extends C {};
new D;
```
While the slack tracking takes care of eventually shrinking the objects
to appropriate sizes, this aggressive over-allocation is still going to
hurt performance quite a bit in the beginning, and will also lead to
more traffic on the minor GC for now good reason.
Instead of the above, we now allocate a minimum of 2 in-object
properties per class (in a hierarchy) and then add a slack of 8 in the
end. Meaning for the example above we end up with 16 initial in-object
property slots, which seems sensible.
Bug: v8:8853
Change-Id: I4a11e35a8612ceef1d776ca2f0543a26c8c2a2bf
Reviewed-on: https://chromium-review.googlesource.com/c/1477276
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59670}
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| benchmarks | ||
| build_overrides | ||
| custom_deps | ||
| docs | ||
| gni | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .clang-tidy | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gn | ||
| .vpython | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| DEPS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| OWNERS | ||
| PRESUBMIT.py | ||
| README.md | ||
| snapshot_toolchain.gni | ||
| WATCHLISTS | ||
V8 JavaScript Engine
V8 is Google's open source JavaScript engine.
V8 implements ECMAScript as specified in ECMA-262.
V8 is written in C++ and is used in Google Chrome, the open source browser from Google.
V8 can run standalone, or can be embedded into any C++ application.
V8 Project page: https://github.com/v8/v8/wiki
Getting the Code
Checkout depot tools, and run
fetch v8
This will checkout V8 into the directory v8 and fetch all of its dependencies.
To stay up to date, run
git pull origin
gclient sync
For fetching all branches, add the following into your remote
configuration in .git/config:
fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
fetch = +refs/tags/*:refs/tags/*
Contributing
Please follow the instructions mentioned on the V8 wiki.