8224847: gc/stress/TestReclaimStringsLeaksMemory.java fails with reserved greater than expected

Summary: Rehash threshold was too low for StringTable, and rehashed size table was too large.
Reviewed-by: rehn, gziemski

src/hotspot/share/classfile/stringTable.cpp

@@ -57,8 +57,8 @@
 #define PREF_AVG_LIST_LEN   2
 // 2^24 is max size
 #define END_SIZE           24
-// If a chain gets to 32 something might be wrong
-#define REHASH_LEN         32
+// If a chain gets to 100 something might be wrong
+#define REHASH_LEN         100
 // If we have as many dead items as 50% of the number of bucket
 #define CLEAN_DEAD_HIGH_WATER_MARK 0.5
 
@@ -558,8 +558,9 @@ bool StringTable::do_rehash() {
     return false;
   }
 
-  // We use max size
-  StringTableHash* new_table = new StringTableHash(END_SIZE, END_SIZE, REHASH_LEN);
+  // We use current size, not max size.
+  size_t new_size = _local_table->get_size_log2(Thread::current());
+  StringTableHash* new_table = new StringTableHash(new_size, END_SIZE, REHASH_LEN);
   // Use alt hash from now on
   _alt_hash = true;
   if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {

test/hotspot/jtreg/gc/stress/TestReclaimStringsLeaksMemory.java

@@ -55,7 +55,7 @@ public class TestReclaimStringsLeaksMemory {
     public static void main(String[] args) throws Exception {
         ArrayList<String> baseargs = new ArrayList(Arrays.asList( "-Xms256M",
                                                                   "-Xmx256M",
-                                                                  "-Xlog:gc*",
+                                                                  "-Xlog:gc*,stringtable*=debug:gc.log",
                                                                   "-XX:NativeMemoryTracking=summary",
                                                                   "-XX:+UnlockDiagnosticVMOptions",
                                                                   "-XX:+PrintNMTStatistics" ));
@@ -93,9 +93,19 @@ public class TestReclaimStringsLeaksMemory {
                     lastString = (BaseName + i).intern();
                 }
                 if (++iterations % 5 == 0) {
-                   System.gc();
+                    System.gc();
                 }
             }
+            // Do one last GC and sleep to give ServiceThread a chance to run.
+            System.out.println("One last gc");
+            System.gc();
+            for (int i = 0; i < 100; i++) {
+                try {
+                    Thread.sleep(10);
+                } catch (InterruptedException ex) {
+                }
+            }
+            System.out.println("End of test");
         }
     }
 }