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chore: enable v8_enable_private_mapping_fork_optimization by default #39253

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Aug 28, 2023
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chore: enable v8_enable_private_mapping_fork_optimization by default #39253

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e646b70
chore: enable v8_enable_private_mapping_fork_optimization by default
deepak1556 Jul 27, 2023
38617b0
chore: cherry-pick 292a4a6 from v8
deepak1556 Aug 19, 2023
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4 changes: 4 additions & 0 deletions build/args/all.gn
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Expand Up @@ -56,3 +56,7 @@ v8_builtins_profiling_log_file = ""
# https://chromium.googlesource.com/chromium/src/+/main/docs/dangling_ptr.md
# TODO(vertedinde): hunt down dangling pointers on Linux
enable_dangling_raw_ptr_checks = false

# This flag speeds up the performance of fork/execve on linux systems.
# Ref: https://chromium-review.googlesource.com/c/v8/v8/+/4602858
v8_enable_private_mapping_fork_optimization = true
1 change: 1 addition & 0 deletions patches/v8/.patches
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Expand Up @@ -2,3 +2,4 @@ build_gn.patch
do_not_export_private_v8_symbols_on_windows.patch
fix_build_deprecated_attribute_for_older_msvc_versions.patch
chore_allow_customizing_microtask_policy_per_context.patch
fix_compile_error_on_macos_with_fork_optimization.patch
34 changes: 34 additions & 0 deletions patches/v8/fix_compile_error_on_macos_with_fork_optimization.patch
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@@ -0,0 +1,34 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: deepak1556 <hop2deep@gmail.com>
Date: Tue, 15 Aug 2023 23:59:59 +0900
Subject: fix: compile error on macOS with
v8_enable_private_mapping_fork_optimization=true

Follow-up to https://chromium-review.googlesource.com/c/v8/v8/+/4602858,
we are trying to enable this flag in Electron without any OS conditions in
args.gn which results in a compilation failure on macOS due to the lack of MADV_DONTFORK.

Given that Node.js and Electron both use posix_spawn on macOS which
by default does not copy MAP_JIT locations, it would be safe to isolate
the change only for linux.

Change-Id: I58ad50e557016fa573d7a27f33a60e2e5b7d1804
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4780212
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Deepak Mohan (Robo) <hop2deep@gmail.com>
Cr-Commit-Position: refs/heads/main@{#89557}

diff --git a/src/base/platform/platform-posix.cc b/src/base/platform/platform-posix.cc
index 77fd9e8f6dd5938d38344ffb0074fb70a0969fd9..73cdbdb19df2aecf3046b2bb2b6cb121f4dc5ca7 100644
--- a/src/base/platform/platform-posix.cc
+++ b/src/base/platform/platform-posix.cc
@@ -161,7 +161,7 @@ void* Allocate(void* hint, size_t size, OS::MemoryPermission access,
void* result = mmap(hint, size, prot, flags, kMmapFd, kMmapFdOffset);
if (result == MAP_FAILED) return nullptr;

-#if V8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION
+#if V8_OS_LINUX && V8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION
// This is advisory, so we ignore errors.
madvise(result, size, MADV_DONTFORK);
#endif