Add approximate feature

rusty-boy-sdl/Cargo.toml

@@ -11,14 +11,19 @@ categories = ["embedded", "gaming"]
 keywords = ["embedded", "gameboy", "playdate"]
 readme = "../README.md"
 
+[features]
+approximate = []
+profile = ["nix"]
 
 [dependencies]
 cartridge = { path = "../cartridge" }
 ppu = { path = "../ppu" }
+sm83 = { path = "../sm83" }
 rusty-boy = { path = "../rusty-boy" }
 anyhow = "1.0"
 png = "0.17"
 sdl2 = "0.36"
 clap = { version = "4.5.4", features = ["derive"] }
 env_logger = "0.11.3"
 log = "0.4"
+nix = { version = "0.28", features = ["sched"], optional = true }

rusty-boy-sdl/src/main.rs

@@ -128,7 +128,19 @@ fn save_file(rom_path: &Path, data: &[u8]) -> anyhow::Result<()> {
     Ok(())
 }
 
+#[cfg(feature = "profile")]
+fn configure_sched_affinity() -> anyhow::Result<()> {
+    log::info!("Setting CPU affinity");
+    let mut cpuset = nix::sched::CpuSet::new();
+    cpuset.set(0)?; // Just one cpu
+    nix::sched::sched_setaffinity(nix::unistd::Pid::this(), &cpuset)?;
+    Ok(())
+}
+
 fn main() -> anyhow::Result<()> {
+    #[cfg(feature = "profile")]
+    configure_sched_affinity()?;
+
     env_logger::init();
 
     let args = Args::parse();
@@ -138,6 +150,9 @@ fn main() -> anyhow::Result<()> {
         .map_err(|e| anyhow::format_err!("Invalid cartridge: {}", e))?;
     let mut rusty_boy = RustyBoy::new_with_cartridge(cartridge);
 
+    #[cfg(feature = "approximate")]
+    rusty_boy.configure_cpu_step(sm83::core::Cycles::new(60));
+
     if rusty_boy.supports_battery_backed_ram() {
         attempt_restore_save_file(&mut rusty_boy, &args.rom_path)?;
     }
@@ -217,6 +232,10 @@ fn main() -> anyhow::Result<()> {
 
         let frame = {
             let frame_start = Instant::now();
+
+            #[cfg(feature = "approximate")]
+            rusty_boy.run_until_next_frame(false);
+
             let frame = rusty_boy.run_until_next_frame(true);
             let frame_end = Instant::now();
             load += frame_end - frame_start;
@@ -244,7 +263,13 @@ fn main() -> anyhow::Result<()> {
             }
         }
 
-        next_deadline += Duration::from_nanos(16_666_667); // 60 fps
+        #[cfg(feature = "approximate")]
+        const FRAME_TIME: Duration = Duration::from_nanos(33_333_333); // 30 fps
+        #[cfg(not(feature = "approximate"))]
+        const FRAME_TIME: Duration = Duration::from_nanos(16_666_667); // 60 fps
+
+        next_deadline += FRAME_TIME;
+
         sleep_until(next_deadline);
 
         frame_id += 1;