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Gabriel Charette 954146a5cf Make TimeTicks::Now() high-resolution whenever possible with low-latency.
It was already always high-resolution on POSIX but was never high
resolution on Windows. Windows does support low latency high-resolution
timers for the majority of our user base.

TimeTicks::HighResolutionNow() was only explicitly requested in testing
frameworks. As such I left the call in place but made it DCHECK that
it's running on a Windows machine on which high-resolution clocks are
used. This confirms that none of our test fleet has regressed with this
change (the previous HighResolutionNow() used to be slightly more
aggressive and also do it in a few configurations where we now fallback
to low-resolution now).

This implementation was copied as-is (modulo minor v8 API
compatibility tweaks). These implementations were the same in the
past but had diverged when, sadly, the same bug was fixed separately
years apart, in Chromium and V8:
chromium: https://codereview.chromium.org/1284053004 + https://codereview.chromium.org/2393953003
v8: https://codereview.chromium.org/1304873011

This is a prerequisite to add metrics around parallel task execution
(low-resolution clocks are useless at that level, but we also don't want
to incur high-latency clocks on machines that can't afford it cheaply).

Bug: chromium:807606
Change-Id: Id18e7be895d8431ebd0e565a1bdf358fe7838489
Reviewed-on: https://chromium-review.googlesource.com/897485
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51027}
2018-02-01 11:55:42 +00:00
benchmarks Fix common misspellings 2017-08-02 09:35:28 +00:00
build_overrides [ndk] Change android ndk root for v8 2018-01-11 08:10:33 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
gni [GN][MIPS] Add ldso_path and gcc_target_rpath config on MIPS 2018-01-30 11:51:24 +00:00
gypfiles [gyp] remove unused variables from v8.gyp. 2018-02-01 09:17:18 +00:00
include New API for capturing embedder object graph in heap snapshot. 2018-02-01 08:05:14 +00:00
infra [build] Add configs for new nosnap bots 2018-01-29 16:34:40 +00:00
samples [gyp] move gyp files from src to gypfiles. 2018-01-23 09:54:36 +00:00
src Make TimeTicks::Now() high-resolution whenever possible with low-latency. 2018-02-01 11:55:42 +00:00
test Make TimeTicks::Now() high-resolution whenever possible with low-latency. 2018-02-01 11:55:42 +00:00
testing [gyp] move build targets for tests to gypfiles. 2018-01-30 06:31:00 +00:00
third_party Move detect_v8_host_arch out of gypfiles. 2018-01-31 08:21:01 +00:00
tools [test] Always run with test processors 2018-02-01 10:46:32 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.git-blame-ignore-revs [build] Add DEPS formatting to hyper-blame 2017-10-09 14:08:45 +00:00
.gitignore [build] Enable downloading mips toolchain via runhooks 2018-01-31 14:38:43 +00:00
.gn For building v8 using gn on aix_ppc64, linux_s390x and linux_ppc64(both LE and BE). 2017-05-12 01:35:09 +00:00
.vpython Add a comment for the VPython dep 2017-10-25 12:23:35 +00:00
.ycm_extra_conf.py [ycm] Switch from gnu++11 to gnu++14 2017-11-27 07:48:21 +00:00
AUTHORS Revert "Reland: Reimplement Object.entries/values as CSA to optimize performance." 2018-01-22 09:47:43 +00:00
BUILD.gn [builtins] Add --stress-off-heap-code to test off-heap code 2018-02-01 08:04:09 +00:00
ChangeLog [tools] Merge ChangeLog from latest release 2017-12-19 12:30:56 +00:00
CODE_OF_CONDUCT.md Explicitly state that the Chromium Code of Conduct also applies to V8 2016-03-02 09:51:24 +00:00
codereview.settings Make Gerrit the default code review for V8 2017-06-30 17:37:37 +00:00
DEPS Update V8 DEPS. 2018-02-01 05:00:39 +00:00
LICENSE Updates to the license information of third party components. 2015-06-16 12:37:50 +00:00
LICENSE.fdlibm Add LICENSE.fdlibm for all the fdlibm imported sources. 2016-06-09 07:17:03 +00:00
LICENSE.strongtalk Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.v8 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.valgrind Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
Makefile [gyp] move build targets for tests to gypfiles. 2018-01-30 06:31:00 +00:00
Makefile.android [build] Fix d8-for-Android builds 2016-05-20 12:10:45 +00:00
OWNERS Update top-level OWNERS. 2018-01-19 08:37:12 +00:00
PRESUBMIT.py [gyp] move gyp files from src to gypfiles. 2018-01-23 09:54:36 +00:00
README.md [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
snapshot_toolchain.gni MIPS[64]: Generate snapshots on MIPS big-endian targets 2017-11-24 19:00:32 +00:00
WATCHLISTS Add adamk to a few WATCHLISTS 2017-11-10 21:38:29 +00:00

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.