From f49535f39b0dac7359fb7ae5541ffc47e41b7507 Mon Sep 17 00:00:00 2001 From: Keyhan Vakil Date: Thu, 22 Jun 2023 17:07:18 +0000 Subject: [PATCH] deps: V8: cherry-pick 1a782f6543ae MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Original commit message: [base] add build flag to use MADV_DONTFORK Embedders like Node.js and Electron expose fork(2)/execve(2) to their users. Unfortunately when the V8 heap is very large, these APIs become rather slow on Linux, due to the kernel needing to do all the bookkeeping for the forked process (in clone's dup_mmap and execve's exec_mmap). Of course, this is useless because the forked child thread will never actually need to access the V8 heap. Add a new build flag v8_enable_private_mapping_fork_optimization which marks all pages allocated by OS::Allocate as MADV_DONTFORK. This improves the performance of Node.js's fork/execve combination by 10x on a 600 MB heap. Fixed: v8:7381 Change-Id: Ib649f774d4a932b41886313ce89acc369923699d Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4602858 Commit-Queue: Michael Lippautz Reviewed-by: Michael Lippautz Cr-Commit-Position: refs/heads/main@{#88447} Refs: https://github.com/v8/v8/commit/1a782f6543ae999bf9e497e23042af0b70191f10 PR-URL: https://github.com/nodejs/node/pull/48523 Fixes: https://github.com/nodejs/node/issues/25382 Fixes: https://github.com/nodejs/node/issues/14917 Refs: https://github.com/nodejs/performance/issues/93 Refs: https://github.com/nodejs/performance/issues/89 Reviewed-By: Yagiz Nizipli Reviewed-By: Juan José Arboleda Reviewed-By: Debadree Chatterjee --- common.gypi | 2 +- deps/v8/BUILD.gn | 14 ++++++++++++++ deps/v8/src/base/platform/platform-posix.cc | 6 ++++++ 3 files changed, 21 insertions(+), 1 deletion(-) diff --git a/common.gypi b/common.gypi index 12421a556f1b71..22c9c48c972bd6 100644 --- a/common.gypi +++ b/common.gypi @@ -36,7 +36,7 @@ # Reset this number to 0 on major V8 upgrades. # Increment by one for each non-official patch applied to deps/v8. - 'v8_embedder_string': '-node.4', + 'v8_embedder_string': '-node.5', ##### V8 defaults for Node.js ##### diff --git a/deps/v8/BUILD.gn b/deps/v8/BUILD.gn index c13cf053a80d21..00c6e42573d372 100644 --- a/deps/v8/BUILD.gn +++ b/deps/v8/BUILD.gn @@ -83,6 +83,17 @@ declare_args() { # Sets -dENABLE_HUGEPAGE v8_enable_hugepage = false + # Sets -dV8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION. + # + # This flag speeds up the performance of fork/execve on Linux systems for + # embedders which use it (like Node.js). It works by marking the pages that + # V8 allocates as MADV_DONTFORK. Without MADV_DONTFORK, the Linux kernel + # spends a long time manipulating page mappings on fork and exec which the + # child process doesn't generally need to access. + # + # See v8:7381 for more details. + v8_enable_private_mapping_fork_optimization = false + # Sets -dENABLE_HANDLE_ZAPPING. v8_enable_handle_zapping = is_asan || is_debug @@ -1002,6 +1013,9 @@ config("features") { if (v8_enable_hugepage) { defines += [ "ENABLE_HUGEPAGE" ] } + if (v8_enable_private_mapping_fork_optimization) { + defines += [ "V8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION" ] + } if (v8_enable_object_print) { defines += [ "OBJECT_PRINT" ] } diff --git a/deps/v8/src/base/platform/platform-posix.cc b/deps/v8/src/base/platform/platform-posix.cc index 2dd97bee02c01f..5408413e11efdd 100644 --- a/deps/v8/src/base/platform/platform-posix.cc +++ b/deps/v8/src/base/platform/platform-posix.cc @@ -160,6 +160,12 @@ void* Allocate(void* hint, size_t size, OS::MemoryPermission access, int flags = GetFlagsForMemoryPermission(access, page_type); void* result = mmap(hint, size, prot, flags, kMmapFd, kMmapFdOffset); if (result == MAP_FAILED) return nullptr; + +#if V8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION + // This is advisory, so we ignore errors. + madvise(result, size, MADV_DONTFORK); +#endif + #if ENABLE_HUGEPAGE if (result != nullptr && size >= kHugePageSize) { const uintptr_t huge_start =