fix: limit concurrent thumbnail generation (#1138)

Cargo.lock

@@ -1537,6 +1537,7 @@ dependencies = [
  "mime_guess",
  "notify-debouncer-full",
  "notify-rust",
+ "num_cpus",
  "once_cell",
  "open",
  "ordermap",

Cargo.toml

@@ -71,6 +71,7 @@ uzers = "0.12.1"
 md-5 = "0.10.6"
 png = "0.17.16"
 jxl-oxide = { version = "0.12.2", features = ["image"] }
+num_cpus = "1.17.0"
 
 # Completion-based IO runtime to enable io_uring / IOCP file IO support.
 [dependencies.compio]

src/tab.rs

@@ -95,6 +95,11 @@ const MAX_SEARCH_RESULTS: usize = 200;
 //TODO: configurable thumbnail size?
 const THUMBNAIL_SIZE: u32 = (ICON_SIZE_GRID as u32) * (ICON_SCALE_MAX as u32);
 
+pub static THUMB_SEMAPHORE: LazyLock<tokio::sync::Semaphore> = LazyLock::new(|| {
+    tokio::sync::Semaphore::const_new(num_cpus::get())
+});
+
+
 pub(crate) static SORT_OPTION_FALLBACK: LazyLock<HashMap<String, (HeadingOptions, bool)>> =
     LazyLock::new(|| {
         HashMap::from_iter(dirs::download_dir().into_iter().map(|dir| {
@@ -5634,6 +5639,7 @@ impl Tab {
                             let message = {
                                 let path = path.clone();
 
+                                _ = THUMB_SEMAPHORE.acquire().await;
                                 tokio::task::spawn_blocking(move || {
                                     let start = Instant::now();
                                     let thumbnail = ItemThumbnail::new(