[platform] Use more tasks for jobs

Wasm recently switched from spawning a number of background tasks for
compilation to just using a single job (via the pretty new
{Platform::PostJob} API). This caused major regressions in several
benchmarks running in d8, because the {DefaultPlatform} is only using
half of the available worker threads for executing jobs with "user
visible" priority.

This CL changes this to use all available worker threads for "user
blocking" or "user visible" jobs, and two threads for "best effort"
jobs. The limit of two threads for best effort is identical to what
chromium does with best effort *tasks*. For user blocking and user
visible, chromium does not impose any limit, so we also remove the
limitation to half of the threads from d8.

Drive-by: Use {NewDefaultJobHandle} for constructing {DefaultJobHandle}.

R=mlippautz@chromium.org
CC=ahaas@chromium.org, gab@chromium.org, etiennep@chromium.org

Bug: chromium:1113234, chromium:1101340
Change-Id: I9280e649a1cf3832c562ff7251e8bda0103af111
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2339481
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Auto-Submit: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69265}
1 file changed
tree: ebb28f03a88eb905be4f32fd2b57f24662e1e620
  1. .clang-format
  2. .clang-tidy
  3. .editorconfig
  4. .flake8
  5. .git-blame-ignore-revs
  6. .gitattributes
  7. .gitignore
  8. .gn
  9. .vpython
  10. .ycm_extra_conf.py
  11. AUTHORS
  12. BUILD.gn
  13. CODE_OF_CONDUCT.md
  14. COMMON_OWNERS
  15. DEPS
  16. ENG_REVIEW_OWNERS
  17. INFRA_OWNERS
  18. INTL_OWNERS
  19. LICENSE
  20. LICENSE.fdlibm
  21. LICENSE.strongtalk
  22. LICENSE.v8
  23. LICENSE.valgrind
  24. MIPS_OWNERS
  25. OWNERS
  26. PPC_OWNERS
  27. PRESUBMIT.py
  28. README.md
  29. S390_OWNERS
  30. WATCHLISTS
  31. build_overrides/
  32. codereview.settings
  33. custom_deps/
  34. docs/
  35. gni/
  36. include/
  37. infra/
  38. samples/
  39. src/
  40. test/
  41. testing/
  42. third_party/
  43. tools/
README.md

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.