From e340aeeee010baf2773fd0d50ce59aa55a823de3 Mon Sep 17 00:00:00 2001
From: Guanqiang Han <ghan@openjdk.org>
Date: Wed, 1 Apr 2026 09:12:51 +0000
Subject: [PATCH] 8379174: G1: Too high G1RemSetArrayOfCardsEntriesBase causes
 invalid ergonomic G1RemSetArrayOfCardsEntries

Reviewed-by: tschatzl, iwalulya
---
 src/hotspot/share/gc/g1/g1Arguments.cpp       |  3 +-
 ...tG1RemSetArrayOfCardsEntriesErgoLimit.java | 43 +++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 test/hotspot/jtreg/gc/g1/TestG1RemSetArrayOfCardsEntriesErgoLimit.java

diff --git a/src/hotspot/share/gc/g1/g1Arguments.cpp b/src/hotspot/share/gc/g1/g1Arguments.cpp
index 8bec6e7e86f..c3bbd5a3b52 100644
--- a/src/hotspot/share/gc/g1/g1Arguments.cpp
+++ b/src/hotspot/share/gc/g1/g1Arguments.cpp
@@ -148,8 +148,9 @@ void G1Arguments::initialize_card_set_configuration() {
 
   if (FLAG_IS_DEFAULT(G1RemSetArrayOfCardsEntries)) {
     uint max_cards_in_inline_ptr = G1CardSetConfiguration::max_cards_in_inline_ptr(G1HeapRegion::LogCardsPerRegion);
+    const JVMTypedFlagLimit<uint>* limit = JVMFlagLimit::get_range_at(FLAG_MEMBER_ENUM(G1RemSetArrayOfCardsEntries))->cast<uint>();
     FLAG_SET_ERGO(G1RemSetArrayOfCardsEntries, MAX2(max_cards_in_inline_ptr * 2,
-                                                    G1RemSetArrayOfCardsEntriesBase << region_size_log_mb));
+                                                    MIN2(G1RemSetArrayOfCardsEntriesBase << region_size_log_mb, limit->max())));
   }
 
   // Howl card set container globals.
diff --git a/test/hotspot/jtreg/gc/g1/TestG1RemSetArrayOfCardsEntriesErgoLimit.java b/test/hotspot/jtreg/gc/g1/TestG1RemSetArrayOfCardsEntriesErgoLimit.java
new file mode 100644
index 00000000000..4af09066def
--- /dev/null
+++ b/test/hotspot/jtreg/gc/g1/TestG1RemSetArrayOfCardsEntriesErgoLimit.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8379174
+ * @summary Test for G1 ergonomics deriving an out-of-range
+ *          G1RemSetArrayOfCardsEntries value from G1RemSetArrayOfCardsEntriesBase
+ * @requires vm.gc.G1
+ * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions
+ *                   -XX:+UseG1GC
+ *                   -XX:G1RemSetArrayOfCardsEntriesBase=62117
+ *                   -XX:G1HeapRegionSize=4m
+ *                   ${test.main.class}
+ */
+
+package gc.g1;
+
+public class TestG1RemSetArrayOfCardsEntriesErgoLimit {
+    public static void main(String[] args) {
+        System.out.println("passed");
+    }
+}