From 3b802a542fa0583c924e04790f71d850e149cf21 Mon Sep 17 00:00:00 2001
From: Serkyo <serkyo-dev@proton.me>
Date: Tue, 7 Jul 2026 17:17:54 +0200
Subject: [PATCH] perf(server): parallelize chunk generation in load_around

---
 Cargo.lock                        | 46 +++++++++++++++++++++++++++++++
 crates/server/Cargo.toml          |  1 +
 crates/server/src/world_server.rs | 27 ++++++++++++++----
 3 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index ac09b17..f783dff 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -335,6 +335,25 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5181e0de7b61eb03a81e347d6dd8797bae9da5146707b51077e2d71a54ec0ceb"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d6914041f254d6e9176c01941b21115dcfb7089e55135a35411081bd106ef3f"
+dependencies = [
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "crossbeam-utils"
 version = "0.8.21"
@@ -374,6 +393,12 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d8b14ccef22fc6f5a8f4d7d768562a182c04ce9a3b3157b91390b52ddfdf1a76"
 
+[[package]]
+name = "either"
+version = "1.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91622ff5e7162018101f2fea40d6ebf4a78bbe5a49736a2020649edf9693679e"
+
 [[package]]
 name = "equivalent"
 version = "1.0.2"
@@ -1192,6 +1217,26 @@ dependencies = [
  "raw-window-handle",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb39b166781f92d482534ef4b4b1b2568f42613b53e5b6c160e24cfbfa30926d"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22e18b0f0062d30d4230b2e85ff77fdfe4326feb054b9783a3460d8435c8ab91"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.4.1"
@@ -1367,6 +1412,7 @@ dependencies = [
 name = "server"
 version = "0.1.0"
 dependencies = [
+ "rayon",
  "serde_json",
  "shared",
  "tracing",
diff --git a/crates/server/Cargo.toml b/crates/server/Cargo.toml
index 1e8d42f..d82985f 100644
--- a/crates/server/Cargo.toml
+++ b/crates/server/Cargo.toml
@@ -9,6 +9,7 @@ authors.workspace = true
 workspace = true
 
 [dependencies]
+rayon = "1.12.0"
 serde_json = "1.0.149"
 shared = { version = "0.1.0", path = "../shared" }
 tracing = "0.1.44"
diff --git a/crates/server/src/world_server.rs b/crates/server/src/world_server.rs
index 5215144..c71ef5d 100644
--- a/crates/server/src/world_server.rs
+++ b/crates/server/src/world_server.rs
@@ -2,6 +2,7 @@
 
 //! Authoritative chunk storage and generation logic for the server.
 
+use rayon::prelude::*;
 use shared::{
     generator::VoxelGenerator,
     world::{Chunk, ChunkPos},
@@ -35,9 +36,8 @@ impl ServerWorld {
     pub fn load_around(&mut self, center_x: f64, center_y: f64, center_z: f64, radius: i32) {
         let center = ChunkPos::from_world(center_x, center_y, center_z);
 
-        // Counts the chunks inside the cylinder that were generated or already resident.
-        let mut count = 0;
-
+        // Phase 1: collect the positions inside the cylinder that are not yet resident
+        let mut pending = Vec::new();
         for x in center.x - radius..=center.x + radius {
             for z in center.z - radius..=center.z + radius {
                 for y in center.y - radius / 2..=center.y + radius / 2 {
@@ -45,13 +45,28 @@ impl ServerWorld {
                     let dz = z - center.z;
 
                     if (dx * dx + dz * dz) <= radius * radius {
-                        self.get_chunk(ChunkPos::new(x, y, z));
-                        count += 1;
+                        let pos = ChunkPos::new(x, y, z);
+                        if !self.chunks.contains_key(&pos) {
+                            pending.push(pos);
+                        }
                     }
                 }
             }
         }
 
-        tracing::info!(chunks = count, center = ?center, radius, "loaded chunk cylinder");
+        // Phase 2: generate the missing chunks in parallel
+        let generator = &self.generator;
+        let generated: Vec<(ChunkPos, Chunk)> = pending
+            .into_par_iter()
+            .map(|pos| (pos, generator.generate_chunk(pos)))
+            .collect();
+
+        // Phase 3: move the finished chunks into the map
+        let count = generated.len();
+        for (pos, chunk) in generated {
+            self.chunks.insert(pos, chunk);
+        }
+
+        tracing::info!(chunks = count, center = ?center, radius, "generated chunk cylinder");
     }
 }