From a19bd458c4f45bd5b79ae4a1463243f5d739f4cf Mon Sep 17 00:00:00 2001
From: joshua-spacetime <josh@clockworklabs.io>
Date: Tue, 10 Jun 2025 10:46:52 -0700
Subject: [PATCH] Reserve cores 0 and 1 for the OS (#2851)

---
 crates/core/src/startup.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/crates/core/src/startup.rs b/crates/core/src/startup.rs
index 57d9f7177e..0dc9476032 100644
--- a/crates/core/src/startup.rs
+++ b/crates/core/src/startup.rs
@@ -1,5 +1,6 @@
 use core_affinity::CoreId;
 use crossbeam_queue::ArrayQueue;
+use itertools::Itertools;
 use spacetimedb_paths::server::{ConfigToml, LogsDir};
 use std::path::PathBuf;
 use std::time::Duration;
@@ -194,7 +195,14 @@ pub struct Cores {
 impl Cores {
     fn get() -> Option<Self> {
         let cores = &mut core_affinity::get_core_ids()
-            .filter(|cores| cores.len() >= 8)?
+            .filter(|cores| cores.len() >= 10)?
+            .into_iter()
+            // We reserve the first two cores for the OS.
+            // This allows us to pin interrupt handlers (IRQs) to these cores,
+            // particularly those for incoming network traffic,
+            // preventing them from preempting the main reducer threads.
+            .filter(|core_id| core_id.id > 1)
+            .collect_vec()
             .into_iter();
 
         let total = cores.len() as f64;