From 28a3e9f724ddb0b9a2e880829805992b08d33559 Mon Sep 17 00:00:00 2001
From: not-matthias <matthias@codspeed.io>
Date: Wed, 23 Apr 2025 18:10:41 +0200
Subject: [PATCH] feat: pin tokio worker threads to core 0

---
 Cargo.lock  | 28 ++++++++++++++++++++++++++++
 Cargo.toml  |  3 ++-
 src/main.rs | 25 +++++++++++++++++++++++--
 3 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index d3e473d0..e76af897 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -266,6 +266,7 @@ dependencies = [
  "base64",
  "clap",
  "console",
+ "core_affinity",
  "git2",
  "gql_client",
  "indicatif",
@@ -328,6 +329,17 @@ version = "0.8.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
 
+[[package]]
+name = "core_affinity"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a034b3a7b624016c6e13f5df875747cc25f884156aad2abd12b6c46797971342"
+dependencies = [
+ "libc",
+ "num_cpus",
+ "winapi",
+]
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.16"
@@ -681,6 +693,12 @@ version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
+[[package]]
+name = "hermit-abi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d231dfb89cfffdbc30e7fc41579ed6066ad03abda9e567ccafae602b97ec5024"
+
 [[package]]
 name = "hex"
 version = "0.4.3"
@@ -1214,6 +1232,16 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "num_cpus"
+version = "1.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4161fcb6d602d4d2081af7c3a45852d875a03dd337a6bfdd6e06407b61342a43"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "number_prefix"
 version = "0.4.0"
diff --git a/Cargo.toml b/Cargo.toml
index c1d026ec..793400f3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -29,7 +29,7 @@ serde = { version = "1.0.192", features = ["derive"] }
 serde_json = { version = "1.0.108", features = ["preserve_order"] }
 url = "2.4.1"
 sha256 = "1.4.0"
-tokio = { version = "1", features = ["macros", "rt"] }
+tokio = { version = "1", features = ["macros", "rt", "rt-multi-thread"] }
 tokio-tar = "0.3.1"
 md5 = "0.7.0"
 base64 = "0.21.0"
@@ -46,6 +46,7 @@ sysinfo = { version = "0.33.1", features = ["serde"] }
 indicatif = "0.17.8"
 console = "0.15.8"
 async-trait = "0.1.82"
+core_affinity = "0.8.3"
 
 [dev-dependencies]
 temp-env = { version = "0.3.6", features = ["async_closure"] }
diff --git a/src/main.rs b/src/main.rs
index ddc57bef..d1ffc5fb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,6 +10,7 @@ mod run;
 mod setup;
 
 use console::style;
+use core_affinity::CoreId;
 use lazy_static::lazy_static;
 use local_logger::clean_logger;
 use prelude::*;
@@ -27,8 +28,28 @@ lazy_static! {
         format!("{VALGRIND_CODSPEED_BASE_VERSION}-0codspeed1");
 }
 
-#[tokio::main(flavor = "current_thread")]
-async fn main() {
+fn main() -> anyhow::Result<()> {
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(4)
+        .on_thread_start(|| {
+            // Core 0 is also responsible for interrupts and other system tasks. But
+            // this is fine, as we're not executing performance-critical code.
+            if !core_affinity::set_for_current(CoreId { id: 0 }) {
+                panic!("failed to pin worker thread to core 0");
+            }
+        })
+        .enable_all()
+        .build()?;
+
+    // NOTE: The code above doesn't set the core affinity for the main thread. We should avoid doing so, as
+    // the affinity is passed down to child threads/processes.
+
+    let _guard = runtime.enter();
+    runtime.block_on(real_main());
+    Ok(())
+}
+
+async fn real_main() {
     let res = crate::app::run().await;
     if let Err(err) = res {
         for cause in err.chain() {