rt: set worker thread count

use at least 2 but at most 4 worker threads

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

Cargo.toml

@@ -12,9 +12,10 @@ homepage = "https://www.proxmox.com"
 exclude = [ "build", "debian" ]
 
 [dependencies]
-bitflags = "1.2"
 anyhow = "1.0"
+bitflags = "1.2"
 lazy_static = "1.4"
 libc = "0.2"
 nix = "0.24"
+num_cpus = "1"
 tokio = { version = "1.0", features = [ "rt-multi-thread", "io-util", "net" ] }

src/main.rs

@@ -101,7 +101,13 @@ fn main() {
         }
     };
 
-    let rt = tokio::runtime::Runtime::new().expect("failed to spawn tokio runtime");
+    let cpus = num_cpus::get();
+
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .enable_all()
+        .worker_threads(cpus.max(2).min(4))
+        .build()
+        .expect("failed to spawn tokio runtime");
 
     if let Err(err) = rt.block_on(do_main(use_sd_notify, path)) {
         eprintln!("error: {}", err);