fix: auto tune of MAX_PAGE_RAM

Fixed issue #3580

Author: lvca

engine/src/main/java/com/arcadedb/GlobalConfiguration.java

@@ -137,19 +137,20 @@ public Object call(final Object value) {
           final long maxRAM = ((long) value) * 1024 * 1024; // VALUE IN MB
 
           if (maxRAM > Runtime.getRuntime().maxMemory() * 80 / 100) {
-            final long newValue = Runtime.getRuntime().maxMemory() / 2;
+            final long newValueBytes = Runtime.getRuntime().maxMemory() / 2;
+            final long newValueMB = newValueBytes / 1024 / 1024;
             if (LogManager.instance() != null)
               LogManager.instance()
                   .log(this, Level.WARNING, "Setting '%s=%s' is > than 80%% of maximum heap (%s). Decreasing it to %s",
                       MAX_PAGE_RAM.key, FileUtils.getSizeAsString(maxRAM),
-                      FileUtils.getSizeAsString(Runtime.getRuntime().maxMemory()), FileUtils.getSizeAsString(newValue));
+                      FileUtils.getSizeAsString(Runtime.getRuntime().maxMemory()), FileUtils.getSizeAsString(newValueBytes));
             else
               System.out.println(
                   "Setting '%s=%s' is > than 80%% of maximum heap (%s). Decreasing it to %s".formatted(MAX_PAGE_RAM.key,
                       FileUtils.getSizeAsString(maxRAM), FileUtils.getSizeAsString(Runtime.getRuntime().maxMemory()),
-                      FileUtils.getSizeAsString(newValue)));
+                      FileUtils.getSizeAsString(newValueBytes)));
 
-            return newValue;
+            return newValueMB;
           }
           return value;
         }

engine/src/test/java/com/arcadedb/GlobalConfigurationTest.java

@@ -24,6 +24,46 @@
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 class GlobalConfigurationTest extends TestHelper {
+  @Test
+  void maxPageRAMAutoTune() {
+    final long originalValue = GlobalConfiguration.MAX_PAGE_RAM.getValueAsLong();
+
+    try {
+      // When reset (no explicit value), maxPageRAM should be auto-tuned to ~25% of max heap
+      GlobalConfiguration.MAX_PAGE_RAM.reset();
+      final long autoTunedMB = GlobalConfiguration.MAX_PAGE_RAM.getValueAsLong();
+      final long maxHeapMB = Runtime.getRuntime().maxMemory() / 1024 / 1024;
+
+      // Auto-tuned value should be approximately 25% of max heap, in MB
+      assertThat(autoTunedMB).isLessThanOrEqualTo(maxHeapMB);
+      assertThat(autoTunedMB).isEqualTo(Runtime.getRuntime().maxMemory() / 4 / 1024 / 1024);
+    } finally {
+      GlobalConfiguration.MAX_PAGE_RAM.setValue(originalValue);
+    }
+  }
+
+  @Test
+  void maxPageRAMCorrectionReturnsMB() {
+    final long originalValue = GlobalConfiguration.MAX_PAGE_RAM.getValueAsLong();
+
+    try {
+      // Set maxPageRAM to a value exceeding 80% of heap to trigger correction
+      final long maxHeapMB = Runtime.getRuntime().maxMemory() / 1024 / 1024;
+      final long excessiveValueMB = maxHeapMB; // 100% of heap, definitely > 80%
+
+      GlobalConfiguration.MAX_PAGE_RAM.setValue(excessiveValueMB);
+      final long correctedValue = GlobalConfiguration.MAX_PAGE_RAM.getValueAsLong();
+
+      // The corrected value must be in MB (should be ~50% of heap in MB)
+      // Before the fix, this would return bytes instead of MB
+      final long expectedMB = Runtime.getRuntime().maxMemory() / 2 / 1024 / 1024;
+      assertThat(correctedValue).isEqualTo(expectedMB);
+      assertThat(correctedValue).isLessThanOrEqualTo(maxHeapMB);
+    } finally {
+      GlobalConfiguration.MAX_PAGE_RAM.setValue(originalValue);
+    }
+  }
+
   @Test
   void serverMode() {
     final String original = GlobalConfiguration.SERVER_MODE.getValueAsString();