perf: Remove RcCharacterStyles::Default, allow enum niche optimisation

aidanhs · aidanhs · commit 7ed840bb69d9 · 2023-12-30T17:30:08.000Z
This reduces TerminalCharacter from 24 to 16 bytes

With a 10MB single line catted into a fresh terminal, VmRSS goes from
478396 kB to 398108 kB (as reported by /proc/&lt;pid&gt;/status) before/after
this patch

Given a 10MB line catted into the terminal, a toggle-fullscreen +
toggle-fullscreen + close-pane + `run true` goes from ~7s to ~4.75s
diff --git a/zellij-server/src/output/mod.rs b/zellij-server/src/output/mod.rs
@@ -6,7 +6,7 @@ use crate::panes::Row;
 use crate::{
     panes::sixel::SixelImageStore,
     panes::terminal_character::{AnsiCode, CharacterStyles},
-    panes::{LinkHandler, TerminalCharacter, EMPTY_TERMINAL_CHARACTER},
+    panes::{LinkHandler, TerminalCharacter, DEFAULT_STYLES, EMPTY_TERMINAL_CHARACTER},
     ClientId,
 };
 use std::cell::RefCell;
@@ -92,7 +92,7 @@ fn serialize_chunks_with_newlines(
     for character_chunk in character_chunks {
         let chunk_changed_colors = character_chunk.changed_colors();
         let mut character_styles =
-            CharacterStyles::new().enable_styled_underlines(styled_underlines);
+            DEFAULT_STYLES.enable_styled_underlines(styled_underlines);
         vte_output.push_str("\n\r");
         let mut chunk_width = character_chunk.x;
         for t_character in character_chunk.terminal_characters.iter() {
@@ -132,7 +132,7 @@ fn serialize_chunks(
     for character_chunk in character_chunks {
         let chunk_changed_colors = character_chunk.changed_colors();
         let mut character_styles =
-            CharacterStyles::new().enable_styled_underlines(styled_underlines);
+            DEFAULT_STYLES.enable_styled_underlines(styled_underlines);
         vte_goto_instruction(character_chunk.x, character_chunk.y, &mut vte_output)
             .with_context(err_context)?;
         let mut chunk_width = character_chunk.x;
diff --git a/zellij-server/src/panes/terminal_character.rs b/zellij-server/src/panes/terminal_character.rs
@@ -36,9 +36,9 @@ pub const RESET_STYLES: CharacterStyles = CharacterStyles {
     styled_underlines_enabled: false,
 };
 
-// Have to manually write this out because Default::default
-// is not a const fn
-const DEFAULT_STYLES: CharacterStyles = CharacterStyles {
+// Prefer to use RcCharacterStyles::default() where it makes sense
+// as it will reduce memory usage
+pub const DEFAULT_STYLES: CharacterStyles = CharacterStyles {
     foreground: None,
     background: None,
     underline_color: None,
@@ -55,6 +55,11 @@ const DEFAULT_STYLES: CharacterStyles = CharacterStyles {
     styled_underlines_enabled: false,
 };
 
+thread_local! {
+    static RC_DEFAULT_STYLES: RcCharacterStyles =
+        RcCharacterStyles::Rc(Rc::new(DEFAULT_STYLES));
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum AnsiCode {
     On,
@@ -149,32 +154,36 @@ impl NamedColor {
     }
 }
 
-#[derive(Clone, Debug, Default, PartialEq)]
+// This enum carefully only has two variants so
+// enum niche optimisations can keep it to 8 bytes
+#[derive(Clone, Debug, PartialEq)]
 pub enum RcCharacterStyles {
-    #[default]
-    Default,
     Reset,
     Rc(Rc<CharacterStyles>),
 }
+const _: [(); 8] = [(); std::mem::size_of::<RcCharacterStyles>()];
 
 impl From<CharacterStyles> for RcCharacterStyles {
     fn from(styles: CharacterStyles) -> Self {
-        if styles == DEFAULT_STYLES {
-            RcCharacterStyles::Default
-        } else if styles == RESET_STYLES {
+        if styles == RESET_STYLES {
             RcCharacterStyles::Reset
         } else {
             RcCharacterStyles::Rc(Rc::new(styles))
         }
     }
 }
 
+impl Default for RcCharacterStyles {
+    fn default() -> Self {
+        RC_DEFAULT_STYLES.with(|s| s.clone())
+    }
+}
+
 impl std::ops::Deref for RcCharacterStyles {
     type Target = CharacterStyles;
 
     fn deref(&self) -> &Self::Target {
         match self {
-            RcCharacterStyles::Default => &DEFAULT_STYLES,
             RcCharacterStyles::Reset => &RESET_STYLES,
             RcCharacterStyles::Rc(styles) => &*styles,
         }
@@ -189,6 +198,10 @@ impl Display for RcCharacterStyles {
 }
 
 impl RcCharacterStyles {
+    pub fn reset() -> Self {
+        Self::Reset
+    }
+
     pub fn update(&mut self, f: impl FnOnce(&mut CharacterStyles)) {
         let mut styles: CharacterStyles = **self;
         f(&mut styles);
@@ -214,12 +227,6 @@ pub struct CharacterStyles {
     pub styled_underlines_enabled: bool,
 }
 
-impl Default for CharacterStyles {
-    fn default() -> Self {
-        DEFAULT_STYLES
-    }
-}
-
 impl PartialEq for CharacterStyles {
     fn eq(&self, other: &Self) -> bool {
         self.foreground == other.foreground
@@ -239,9 +246,6 @@ impl PartialEq for CharacterStyles {
 }
 
 impl CharacterStyles {
-    pub fn new() -> Self {
-        Self::default()
-    }
     pub fn foreground(mut self, foreground_code: Option<AnsiCode>) -> Self {
         self.foreground = foreground_code;
         self
@@ -329,7 +333,7 @@ impl CharacterStyles {
 
         // create diff from all changed styles
         let mut diff =
-            CharacterStyles::new().enable_styled_underlines(self.styled_underlines_enabled);
+            DEFAULT_STYLES.enable_styled_underlines(self.styled_underlines_enabled);
 
         if self.foreground != new_styles.foreground {
             diff.foreground = new_styles.foreground;
@@ -388,7 +392,7 @@ impl CharacterStyles {
         }
         Some(diff)
     }
-    pub fn reset_all(&mut self) {
+    fn reset_all(&mut self) {
         self.foreground = Some(AnsiCode::Reset);
         self.background = Some(AnsiCode::Reset);
         self.underline_color = Some(AnsiCode::Reset);
@@ -917,6 +921,9 @@ pub struct TerminalCharacter {
     pub styles: RcCharacterStyles,
     width: u8,
 }
+// This size has significant memory and CPU implications for long lines,
+// be careful about allowing it to grow
+const _: [(); 16] = [(); std::mem::size_of::<TerminalCharacter>()];
 
 impl TerminalCharacter {
     #[inline]
diff --git a/zellij-server/src/ui/pane_boundaries_frame.rs b/zellij-server/src/ui/pane_boundaries_frame.rs
@@ -1,5 +1,5 @@
 use crate::output::CharacterChunk;
-use crate::panes::{AnsiCode, CharacterStyles, TerminalCharacter, EMPTY_TERMINAL_CHARACTER};
+use crate::panes::{AnsiCode, RcCharacterStyles, TerminalCharacter, EMPTY_TERMINAL_CHARACTER};
 use crate::ui::boundaries::boundary_type;
 use crate::ClientId;
 use zellij_utils::data::{client_id_to_colors, PaletteColor, Style};
@@ -11,22 +11,17 @@ use unicode_width::{UnicodeWidthChar, UnicodeWidthStr};
 fn foreground_color(characters: &str, color: Option<PaletteColor>) -> Vec<TerminalCharacter> {
     let mut colored_string = Vec::new();
     for character in characters.chars() {
-        let styles = match color {
-            Some(palette_color) => {
-                let mut styles = CharacterStyles::new();
-                styles.reset_all();
-                styles
-                    .foreground(Some(AnsiCode::from(palette_color)))
-                    .bold(Some(AnsiCode::On))
-            },
-            None => {
-                let mut styles = CharacterStyles::new();
-                styles.reset_all();
-                styles.bold(Some(AnsiCode::On))
-            },
-        };
-        let terminal_character =
-            TerminalCharacter::new_styled(character, styles.into());
+        let mut styles = RcCharacterStyles::reset();
+        styles.update(|styles| {
+            styles.bold = Some(AnsiCode::On);
+            match color {
+                Some(palette_color) => {
+                    styles.foreground = Some(AnsiCode::from(palette_color));
+                },
+                None => {},
+            }
+        });
+        let terminal_character = TerminalCharacter::new_styled(character, styles);
         colored_string.push(terminal_character);
     }
     colored_string
@@ -35,22 +30,17 @@ fn foreground_color(characters: &str, color: Option<PaletteColor>) -> Vec<Termin
 fn background_color(characters: &str, color: Option<PaletteColor>) -> Vec<TerminalCharacter> {
     let mut colored_string = Vec::new();
     for character in characters.chars() {
-        let styles = match color {
-            Some(palette_color) => {
-                let mut styles = CharacterStyles::new();
-                styles.reset_all();
-                styles
-                    .background(Some(AnsiCode::from(palette_color)))
-                    .bold(Some(AnsiCode::On))
-            },
-            None => {
-                let mut styles = CharacterStyles::new();
-                styles.reset_all();
-                styles
-            },
-        };
-        let terminal_character =
-            TerminalCharacter::new_styled(character, styles.into());
+        let mut styles = RcCharacterStyles::reset();
+        styles.update(|styles| {
+            match color {
+                Some(palette_color) => {
+                    styles.background = Some(AnsiCode::from(palette_color));
+                    styles.bold(Some(AnsiCode::On));
+                },
+                None => {},
+            }
+        });
+        let terminal_character = TerminalCharacter::new_styled(character, styles);
         colored_string.push(terminal_character);
     }
     colored_string
