From 55dedcc88e5c90c25d1853a0d330ff34261a5fbe Mon Sep 17 00:00:00 2001
From: Daoming Qiu <daoming.qiu@intel.com>
Date: Sat, 27 Aug 2022 17:53:33 +0800
Subject: [PATCH] src: add option to set cpu affinity of mainthread

Add runtime option '--set-mainthread-cpu-affinity' to pin the
mainthread to the current running cpu before entering event loop.
This feature is implemented on Linux OS currently.

Enabling this option will benefit node.js applications running on
heavy-workload system and can increase performance for several
node.js benchmarks, ex., several cases in benchmark/vm/ improved
by 40%.
---
 src/node_main_instance.cc | 16 ++++++++++++++++
 src/node_options.cc       |  7 +++++++
 src/node_options.h        |  1 +
 3 files changed, 24 insertions(+)

diff --git a/src/node_main_instance.cc b/src/node_main_instance.cc
index 12d51743dddaca..99a4f728145ad1 100644
--- a/src/node_main_instance.cc
+++ b/src/node_main_instance.cc
@@ -19,6 +19,10 @@
 #if HAVE_INSPECTOR
 #include "inspector/worker_inspector.h"  // ParentInspectorHandle
 #endif
+#if defined(__linux__)
+#include <sched.h>
+#include <unistd.h>
+#endif
 
 namespace node {
 
@@ -134,6 +138,18 @@ int NodeMainInstance::Run() {
 
 void NodeMainInstance::Run(int* exit_code, Environment* env) {
   if (*exit_code == 0) {
+    if (per_process::cli_options->set_mainthread_cpu_affinity) {
+#if defined(__linux__)
+      cpu_set_t mask;
+      int c = sched_getcpu();
+      if (c >= 0) {
+        CPU_ZERO(&mask);
+        CPU_SET(c, &mask);
+        sched_setaffinity(0, sizeof(cpu_set_t), &mask);
+      }
+#endif
+    }
+
     LoadEnvironment(env, StartExecutionCallback{});
 
     *exit_code = SpinEventLoop(env).FromMaybe(1);
diff --git a/src/node_options.cc b/src/node_options.cc
index 0869cbb974be86..a02b2c03383cc9 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -908,6 +908,13 @@ PerProcessOptionsParser::PerProcessOptionsParser(
             &PerProcessOptions::trace_sigint,
             kAllowedInEnvironment);
 
+  AddOption("--set-mainthread-cpu-affinity",
+            "enable setting mainthread's cpu affinity to the currently "
+            "running cpu before entering event loop, implemented on "
+            "Linux OS only",
+            &PerProcessOptions::set_mainthread_cpu_affinity,
+            kAllowedInEnvironment);
+
   Insert(iop, &PerProcessOptions::get_per_isolate_options);
 
   AddOption("--node-memory-debug",
diff --git a/src/node_options.h b/src/node_options.h
index ca43192d85a4b4..11264f94e75842 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -283,6 +283,7 @@ class PerProcessOptions : public Options {
   // TODO(addaleax): Some of these could probably be per-Environment.
   std::string use_largepages = "off";
   bool trace_sigint = false;
+  bool set_mainthread_cpu_affinity = false;
   std::vector<std::string> cmdline;
 
   inline PerIsolateOptions* get_per_isolate_options();