From 62e6c11e6e4e4d0cf5f4c380219fe10129bb2694 Mon Sep 17 00:00:00 2001
From: jneufeld <jneufeld@google.com>
Date: Tue, 24 Jul 2018 13:01:33 -0700
Subject: [PATCH] A couple tweaks to ModelLoaderRegistry to improve potential
 contention.

1) Synchronize only the inner method that accesses the cache, as the outer call
that loops and filters the loaders appears to not have threading issues.
2) Probably less of an impact since I imagine the loops are generally small,
but only allocate an ArrayList once you find a matching loader, and allocate it
with size - i which is the max possible remaining in the loop, rather than
always allocating it to size.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=205877123
---
 .../glide/load/model/ModelLoaderRegistry.java        | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/library/src/main/java/com/bumptech/glide/load/model/ModelLoaderRegistry.java b/library/src/main/java/com/bumptech/glide/load/model/ModelLoaderRegistry.java
index ef11d7a211..0b52d387e0 100644
--- a/library/src/main/java/com/bumptech/glide/load/model/ModelLoaderRegistry.java
+++ b/library/src/main/java/com/bumptech/glide/load/model/ModelLoaderRegistry.java
@@ -67,14 +67,19 @@ private <Model, Data> void tearDown(
   }
 
   @NonNull
-  public synchronized <A> List<ModelLoader<A, ?>> getModelLoaders(@NonNull A model) {
+  public <A> List<ModelLoader<A, ?>> getModelLoaders(@NonNull A model) {
     List<ModelLoader<A, ?>> modelLoaders = getModelLoadersForClass(getClass(model));
     int size = modelLoaders.size();
-    List<ModelLoader<A, ?>> filteredLoaders = new ArrayList<>(size);
+    boolean isEmpty = true;
+    List<ModelLoader<A, ?>> filteredLoaders = Collections.emptyList();
     //noinspection ForLoopReplaceableByForEach to improve perf
     for (int i = 0; i < size; i++) {
       ModelLoader<A, ?> loader = modelLoaders.get(i);
       if (loader.handles(model)) {
+        if (isEmpty) {
+          filteredLoaders = new ArrayList<>(size - i);
+          isEmpty = false;
+        }
         filteredLoaders.add(loader);
       }
     }
@@ -92,7 +97,8 @@ public synchronized List<Class<?>> getDataClasses(@NonNull Class<?> modelClass)
   }
 
   @NonNull
-  private <A> List<ModelLoader<A, ?>> getModelLoadersForClass(@NonNull Class<A> modelClass) {
+  private synchronized <A> List<ModelLoader<A, ?>> getModelLoadersForClass(
+      @NonNull Class<A> modelClass) {
     List<ModelLoader<A, ?>> loaders = cache.get(modelClass);
     if (loaders == null) {
       loaders = Collections.unmodifiableList(multiModelLoaderFactory.build(modelClass));