From f59eb77252d1730319d532fc0a0c50ce860edd9d Mon Sep 17 00:00:00 2001
From: Michael Aaron Murphy <michael@mmurphy.dev>
Date: Wed, 12 Feb 2025 18:30:32 +0100
Subject: [PATCH] perf: set static mmap threshold on gnu target env by default

---
 src/app/mod.rs      |  6 +++++-
 src/app/settings.rs |  4 ++++
 src/applet/mod.rs   |  8 +++++---
 src/lib.rs          |  8 ++++++--
 src/malloc.rs       | 14 ++++++++++++++
 5 files changed, 34 insertions(+), 6 deletions(-)
 create mode 100644 src/malloc.rs

diff --git a/src/app/mod.rs b/src/app/mod.rs
index 45b53fc6ea2..58b1c66d1dd 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -138,7 +138,11 @@ pub(crate) fn iced_settings<App: Application>(
 ///
 /// Returns error on application failure.
 pub fn run<App: Application>(settings: Settings, flags: App::Flags) -> iced::Result {
-    let default_font = settings.default_font;
+    #[cfg(target_env = "gnu")]
+    if let Some(threshold) = settings.default_mmap_threshold {
+        crate::malloc::limit_mmap_threshold(threshold);
+    }
+
     let (settings, mut flags, window_settings) = iced_settings::<App>(settings, flags);
     #[cfg(not(feature = "multi-window"))]
     {
diff --git a/src/app/settings.rs b/src/app/settings.rs
index bd8a5f3debb..a5782c9979e 100644
--- a/src/app/settings.rs
+++ b/src/app/settings.rs
@@ -38,6 +38,9 @@ pub struct Settings {
     /// Default size of fonts.
     pub(crate) default_text_size: f32,
 
+    /// Set the default mmap threshold for malloc with mallopt.
+    pub(crate) default_mmap_threshold: Option<i32>,
+
     /// Whether the window should be resizable or not.
     /// and the size of the window border which can be dragged for a resize
     pub(crate) resizable: Option<f64>,
@@ -85,6 +88,7 @@ impl Default for Settings {
             default_font: font::default(),
             default_icon_theme: None,
             default_text_size: 14.0,
+            default_mmap_threshold: Some(128 * 1024),
             resizable: Some(8.0),
             scale_factor: std::env::var("COSMIC_SCALE")
                 .ok()
diff --git a/src/applet/mod.rs b/src/applet/mod.rs
index 4980c91d42b..0ca8a4f1306 100644
--- a/src/applet/mod.rs
+++ b/src/applet/mod.rs
@@ -153,7 +153,6 @@ impl Context {
         self.size = Size::Hardcoded((width, height));
     }
 
-    #[must_use]
     #[allow(clippy::cast_precision_loss)]
     pub fn window_settings(&self) -> crate::app::Settings {
         let (width, height) = self.suggested_size(true);
@@ -183,7 +182,6 @@ impl Context {
         matches!(self.anchor, PanelAnchor::Top | PanelAnchor::Bottom)
     }
 
-    #[must_use]
     pub fn icon_button_from_handle<'a, Message: 'static>(
         &self,
         icon: widget::icon::Handle,
@@ -213,7 +211,6 @@ impl Context {
         .class(Button::AppletIcon)
     }
 
-    #[must_use]
     pub fn icon_button<'a, Message: 'static>(
         &self,
         icon_name: &'a str,
@@ -385,6 +382,11 @@ pub fn run<App: Application>(flags: App::Flags) -> iced::Result {
     let mut settings = helper.window_settings();
     settings.resizable = None;
 
+    #[cfg(target_env = "gnu")]
+    if let Some(threshold) = settings.default_mmap_threshold {
+        crate::malloc::limit_mmap_threshold(threshold);
+    }
+
     if let Some(icon_theme) = settings.default_icon_theme.clone() {
         crate::icon_theme::set_default(icon_theme);
     }
diff --git a/src/lib.rs b/src/lib.rs
index 3e583d131fa..bd4651ace1b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,6 +33,9 @@ pub use cosmic_config;
 #[doc(inline)]
 pub use cosmic_theme;
 
+#[cfg(feature = "desktop")]
+pub mod desktop;
+
 #[cfg(any(feature = "xdg-portal", feature = "rfd"))]
 pub mod dialog;
 
@@ -73,8 +76,9 @@ pub use iced_wgpu;
 pub mod icon_theme;
 pub mod keyboard_nav;
 
-#[cfg(feature = "desktop")]
-pub mod desktop;
+#[cfg(target_env = "gnu")]
+pub(crate) mod malloc;
+
 #[cfg(all(feature = "process", not(windows)))]
 pub mod process;
 
diff --git a/src/malloc.rs b/src/malloc.rs
new file mode 100644
index 00000000000..001f9a166c3
--- /dev/null
+++ b/src/malloc.rs
@@ -0,0 +1,14 @@
+use std::os::raw::c_int;
+
+const M_MMAP_THRESHOLD: c_int = -3;
+
+extern "C" {
+    fn mallopt(param: c_int, value: c_int) -> c_int;
+}
+
+/// Prevents glibc from hoarding memory via memory fragmentation.
+pub fn limit_mmap_threshold(threshold: i32) {
+    unsafe {
+        mallopt(M_MMAP_THRESHOLD, threshold as c_int);
+    }
+}