add optional --cpu-priority unchanged

src/configure.rs

@@ -9,7 +9,7 @@ use std::{
     time::Duration,
 };
 
-use clap::{builder::PathBufValueParser, ArgAction, Parser};
+use clap::{builder::PathBufValueParser, ArgAction, Parser, ValueEnum};
 use configparser::ini::Ini;
 use url::Url;
 
@@ -53,6 +53,11 @@ pub struct Opt {
     #[arg(long, alias = "threads", global = true)]
     pub cores: Option<Cores>,
 
+    /// Override CPU scheduling priorty of fishnet and engine processes.
+    /// Very low by default.
+    #[arg(long, global = true)]
+    pub cpu_priority: Option<CpuPriority>,
+
     /// Maximum backoff time. The client will use randomized expontential
     /// backoff when repeatedly receiving no job. Defaults to 30s.
     #[arg(long, global = true)]
@@ -125,6 +130,13 @@ pub struct Verbose {
     pub level: u8,
 }
 
+#[derive(Debug, Default, Copy, Clone, ValueEnum)]
+pub enum CpuPriority {
+    Unchanged,
+    #[default]
+    Min,
+}
+
 #[derive(Debug, Clone)]
 pub struct Key(pub String);
 

src/main.rs

@@ -34,7 +34,7 @@ use tokio::{
 
 use crate::{
     assets::{Assets, ByEngineFlavor, Cpu, EngineFlavor},
-    configure::{Command, Cores, Opt},
+    configure::{Command, Cores, CpuPriority, Opt},
     ipc::{Position, PositionFailed, Pull},
     logger::{Logger, ProgressAt},
     stockfish::StockfishInit,
@@ -170,16 +170,21 @@ async fn run(opt: Opt, logger: &Logger) {
         rx
     };
 
+    // Set scheduling priority.
+    match opt.cpu_priority.unwrap_or_default() {
+        CpuPriority::Unchanged => (),
+        CpuPriority::Min => {
+            if let Err(err) = set_current_thread_priority(ThreadPriority::Min) {
+                logger.warn(&format!("Failed to decrease CPU priority: {err:?}"));
+            }
+        }
+    }
+
     let mut restart = None;
     let mut up_to_date = Instant::now();
     let mut summarized = Instant::now();
     let mut shutdown_soon = false;
 
-    // Decrease CPU priority
-    if set_current_thread_priority(ThreadPriority::Min).is_err() {
-        logger.warn("Failed to set CPU priority");
-    };
-
     loop {
         // Check for updates from time to time.
         let now = Instant::now();

src/systemd.rs

@@ -22,7 +22,6 @@ pub fn systemd_system(opt: Opt) {
         "User={}",
         env::var("USER").unwrap_or_else(|_| "XXX".to_owned())
     );
-    println!("Nice=5");
     println!("CapabilityBoundingSet=");
     println!("PrivateTmp=true");
     println!("PrivateDevices=true");
@@ -64,7 +63,6 @@ pub fn systemd_user(opt: Opt) {
     println!("ExecStart={} run", exec_start(Invocation::Absolute, &opt));
     println!("KillMode=mixed");
     println!("WorkingDirectory=/tmp");
-    println!("Nice=5");
     println!("PrivateTmp=true");
     println!("DevicePolicy=closed");
     if opt.auto_update