f11ba854e5
This adds a new flag --modify-field-representation-inplace (enabled by default), which lets the runtime perform field representation changes for Smi to Tagged or for HeapObject to Tagged in-place instead of creating new maps and marking the previous map tree as deprecated. That means we create (a lot) fewer Maps and DescriptorArrays in the beginning and also need to self-heal fewer objects later (migrating off the deprecated maps). In TurboFan we just take the "field owner dependency" whenever we use the field representation, which is very similar to what we already do for the field types. That means if we change the representation of a field that we used in optimized code, we will simply deoptimize that code and have TurboFan potentially later optimize it again with the new field representation. On the Speedometer2/ElmJS-TodoMVC test, this reduces the total execution time from around 415ms to around 352ms, which corresponds to a **15%** improvement. The overall Speedometer2 score improves from around 74.1 to around 78.3 (on local runs with content_shell), corresponding to a **5.6%** improvement here. 🎉 On the CNN desktop browsing story, it seems that we reduce map space utilization/fragmentation by about 4-5%. But since we allocate a lot less (fewer Maps and DescriptorArrays) we also significantly change the GC timing, which heavily influences the results here. So take this with a grain of salt. 🤷 Note: For Double fields, this doesn't change anything, meaning they still create new maps and deprecate the previous map trees. Bug: v8:8749, v8:8865, v8:9114 Change-Id: Ibd70efcb59be982863905663dbfaa89aa5b31e14 Cq-Include-Trybots: luci.chromium.try:linux-rel,win7-rel Doc: http://bit.ly/v8-in-place-field-representation-changes Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1565891 Commit-Queue: Benedikt Meurer <bmeurer@chromium.org> Commit-Queue: Igor Sheludko <ishell@chromium.org> Auto-Submit: Benedikt Meurer <bmeurer@chromium.org> Reviewed-by: Igor Sheludko <ishell@chromium.org> Cr-Commit-Position: refs/heads/master@{#60822} |
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| 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://v8.dev/docs
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 at v8.dev/docs/contribute.