From 5c30bf27d4473bc01faa1e299f4a501dc6b95cb6 Mon Sep 17 00:00:00 2001
From: Eric Anderson <ejona@google.com>
Date: Fri, 4 Apr 2025 05:16:37 -0700
Subject: [PATCH] core: Avoid Set.removeAll() when passing a possibly-large
 List (#11994)

See #11958
---
 .../main/java/io/grpc/internal/DelayedClientTransport.java  | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/io/grpc/internal/DelayedClientTransport.java b/core/src/main/java/io/grpc/internal/DelayedClientTransport.java
index 8ff755af3eb..eccd8fadc8c 100644
--- a/core/src/main/java/io/grpc/internal/DelayedClientTransport.java
+++ b/core/src/main/java/io/grpc/internal/DelayedClientTransport.java
@@ -325,7 +325,11 @@ final void reprocess(@Nullable SubchannelPicker picker) {
       if (!hasPendingStreams()) {
         return;
       }
-      pendingStreams.removeAll(toRemove);
+      // Avoid pendingStreams.removeAll() as it can degrade to calling toRemove.contains() for each
+      // element in pendingStreams.
+      for (PendingStream stream : toRemove) {
+        pendingStreams.remove(stream);
+      }
       // Because delayed transport is long-lived, we take this opportunity to down-size the
       // hashmap.
       if (pendingStreams.isEmpty()) {