From 4ee73a8793af1d791a5b0ccde7ba62cb3906a079 Mon Sep 17 00:00:00 2001
From: Alula <6276139+alula@users.noreply.github.com>
Date: Mon, 12 Aug 2024 23:08:04 +0200
Subject: [PATCH] Hopefully this will improve I/O perf on Horizon

---
 src/game/settings.rs | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/game/settings.rs b/src/game/settings.rs
index 9a6de88..09ae380 100644
--- a/src/game/settings.rs
+++ b/src/game/settings.rs
@@ -1,3 +1,5 @@
+use std::io::{Read, Write};
+
 use crate::framework::context::Context;
 use crate::framework::error::GameResult;
 use crate::framework::filesystem::{user_create, user_open};
@@ -173,8 +175,13 @@ fn default_cutscene_skip_mode() -> CutsceneSkipMode {
 
 impl Settings {
     pub fn load(ctx: &Context) -> GameResult<Settings> {
-        if let Ok(file) = user_open(ctx, "/settings.json") {
-            match serde_json::from_reader::<_, Settings>(file) {
+        if let Ok(mut file) = user_open(ctx, "/settings.json") {
+            // we use a buffer to avoid hammering the OS with small reads/writes
+            // I/O on settings was particularly VERY SLOW on Horizon (well it's based on microkernel, so IPC overhead...)
+            let mut buf = Vec::new();
+            file.read_to_end(&mut buf)?;
+
+            match serde_json::from_slice::<Settings>(&buf) {
                 Ok(settings) => return Ok(settings.upgrade()),
                 Err(err) => log::warn!("Failed to deserialize settings: {}", err),
             }
@@ -183,6 +190,14 @@ impl Settings {
         Ok(Settings::default())
     }
 
+    pub fn save(&self, ctx: &Context) -> GameResult {
+        // see why in load()
+        let buffer = serde_json::to_vec_pretty(self)?;
+        user_create(ctx, "/settings.json")?.write_all(&buffer)?;
+
+        Ok(())
+    }
+
     fn upgrade(mut self) -> Self {
         let initial_version = self.version;
 
@@ -362,13 +377,6 @@ impl Settings {
         self
     }
 
-    pub fn save(&self, ctx: &Context) -> GameResult {
-        let file = user_create(ctx, "/settings.json")?;
-        serde_json::to_writer_pretty(file, self)?;
-
-        Ok(())
-    }
-
     pub fn create_player1_controller(&self) -> Box<dyn PlayerController> {
         if self.touch_controls {
             return Box::new(TouchPlayerController::new());