From 2756eb419af2210eed3d0574e20a620918e4e577 Mon Sep 17 00:00:00 2001
From: mat <git@matdoes.dev>
Date: Sun, 22 Feb 2026 11:35:41 +0700
Subject: optimizations at high entity counts

---
 azalea-client/src/plugins/packet/mod.rs | 50 +++++++++++++++++++++------------
 1 file changed, 32 insertions(+), 18 deletions(-)

(limited to 'azalea-client/src/plugins/packet/mod.rs')

diff --git a/azalea-client/src/plugins/packet/mod.rs b/azalea-client/src/plugins/packet/mod.rs
index 63a94ee0..4309850e 100644
--- a/azalea-client/src/plugins/packet/mod.rs
+++ b/azalea-client/src/plugins/packet/mod.rs
@@ -11,6 +11,7 @@ use crate::chat::ChatReceivedEvent;
 pub mod config;
 pub mod game;
 pub mod login;
+pub mod relative_updates;
 
 pub struct PacketPlugin;
 
@@ -30,23 +31,27 @@ pub fn death_event_on_0_health(
 
 impl Plugin for PacketPlugin {
     fn build(&self, app: &mut App) {
-        app.add_observer(game::handle_outgoing_packets_observer)
-            .add_observer(config::handle_outgoing_packets_observer)
-            .add_observer(login::handle_outgoing_packets_observer)
-            .add_systems(Update, death_event_on_0_health)
-            .add_message::<game::ReceiveGamePacketEvent>()
-            .add_message::<config::ReceiveConfigPacketEvent>()
-            .add_message::<login::ReceiveLoginPacketEvent>()
-            //
-            .add_message::<game::AddPlayerEvent>()
-            .add_message::<game::RemovePlayerEvent>()
-            .add_message::<game::UpdatePlayerEvent>()
-            .add_message::<ChatReceivedEvent>()
-            .add_message::<game::DeathEvent>()
-            .add_message::<game::KeepAliveEvent>()
-            .add_message::<game::ResourcePackEvent>()
-            .add_message::<game::WorldLoadedEvent>()
-            .add_message::<login::ReceiveCustomQueryEvent>();
+        app.add_systems(
+            Update,
+            relative_updates::debug_detect_updates_received_on_local_entities,
+        )
+        .add_observer(game::handle_outgoing_packets_observer)
+        .add_observer(config::handle_outgoing_packets_observer)
+        .add_observer(login::handle_outgoing_packets_observer)
+        .add_systems(Update, death_event_on_0_health)
+        .add_message::<game::ReceiveGamePacketEvent>()
+        .add_message::<config::ReceiveConfigPacketEvent>()
+        .add_message::<login::ReceiveLoginPacketEvent>()
+        //
+        .add_message::<game::AddPlayerEvent>()
+        .add_message::<game::RemovePlayerEvent>()
+        .add_message::<game::UpdatePlayerEvent>()
+        .add_message::<ChatReceivedEvent>()
+        .add_message::<game::DeathEvent>()
+        .add_message::<game::KeepAliveEvent>()
+        .add_message::<game::ResourcePackEvent>()
+        .add_message::<game::WorldLoadedEvent>()
+        .add_message::<login::ReceiveCustomQueryEvent>();
     }
 }
 
@@ -70,12 +75,21 @@ macro_rules! __declare_packet_handlers {
 
 pub(crate) use __declare_packet_handlers as declare_packet_handlers;
 
+#[derive(Resource)]
+struct CachedSystemState<T: SystemParam + 'static>(SystemState<T>);
+
 pub(crate) fn as_system<T>(ecs: &mut World, f: impl FnOnce(T::Item<'_, '_>))
 where
     T: SystemParam + 'static,
 {
-    let mut system_state = SystemState::<T>::new(ecs);
+    // creating a new SystemState is expensive, so we save them as a Resource in the
+    // ecs
+    let mut system_state = match ecs.remove_resource::<CachedSystemState<T>>() {
+        Some(s) => s.0,
+        None => SystemState::<T>::new(ecs),
+    };
     let values = system_state.get_mut(ecs);
     f(values);
     system_state.apply(ecs);
+    ecs.insert_resource(CachedSystemState(system_state));
 }
-- 
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