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v8: enable maglev on supported architectures
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Enable V8's new maglev compiler by default on supported architectures.
This brings modest performance improvements for short-lived workloads
like CLI programs (see the linked issue) and brings Node.js's
configuration slightly closer to Google Chrome's.

I marked this change as semver-major because Maglev can theoretically
cause performance regressions, although I haven't seen an example of
that in the (somewhat limited) benchmarking I've done.

**Notable Change Summary:** V8's Maglev Compiler is now enabled by
default on supported architectures (https://v8.dev/blog/maglev). Maglev
improves CPU performance for short-lived CLI programs by around 8%.

Fixes: nodejs#50690
PR-URL: nodejs#51360
Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
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kvakil authored and marco-ippolito committed Jan 10, 2024
1 parent c7f8dc4 commit f682c19
Showing 1 changed file with 8 additions and 4 deletions.
12 changes: 8 additions & 4 deletions configure.py
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@
valid_mips_float_abi = ('soft', 'hard')
valid_intl_modes = ('none', 'small-icu', 'full-icu', 'system-icu')
icu_versions = json.loads((tools_path / 'icu' / 'icu_versions.json').read_text(encoding='utf-8'))
maglev_enabled_architectures = ('x64', 'arm', 'arm64')

shareable_builtins = {'cjs_module_lexer/lexer': 'deps/cjs-module-lexer/lexer.js',
'cjs_module_lexer/dist/lexer': 'deps/cjs-module-lexer/dist/lexer.js',
Expand Down Expand Up @@ -812,11 +813,13 @@
help='Enable V8 transparent hugepage support. This feature is only '+
'available on Linux platform.')

parser.add_argument('--v8-enable-maglev',
maglev_enabled_by_default_help = f"(Maglev is enabled by default on {','.join(maglev_enabled_architectures)})"

parser.add_argument('--v8-disable-maglev',
action='store_true',
dest='v8_enable_maglev',
dest='v8_disable_maglev',
default=None,
help='Enable V8 Maglev compiler. Not available on all platforms.')
help=f"Disable V8's Maglev compiler. {maglev_enabled_by_default_help}")

parser.add_argument('--v8-enable-short-builtin-calls',
action='store_true',
Expand Down Expand Up @@ -1498,7 +1501,8 @@ def configure_v8(o):
o['variables']['v8_random_seed'] = 0 # Use a random seed for hash tables.
o['variables']['v8_promise_internal_field_count'] = 1 # Add internal field to promises for async hooks.
o['variables']['v8_use_siphash'] = 0 if options.without_siphash else 1
o['variables']['v8_enable_maglev'] = 1 if options.v8_enable_maglev else 0
o['variables']['v8_enable_maglev'] = B(not options.v8_disable_maglev and
o['variables']['target_arch'] in maglev_enabled_architectures)
o['variables']['v8_enable_pointer_compression'] = 1 if options.enable_pointer_compression else 0
o['variables']['v8_enable_31bit_smis_on_64bit_arch'] = 1 if options.enable_pointer_compression else 0
o['variables']['v8_enable_shared_ro_heap'] = 0 if options.enable_pointer_compression or options.disable_shared_ro_heap else 1
Expand Down

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