8291970: Add TableStatistics get function to ResourceHashtable

Reviewed-by: iklam, ccheung

src/hotspot/share/utilities/resourceHash.hpp

@@ -26,6 +26,8 @@
 #define SHARE_UTILITIES_RESOURCEHASH_HPP
 
 #include "memory/allocation.hpp"
+#include "utilities/numberSeq.hpp"
+#include "utilities/tableStatistics.hpp"
 
 template<typename K, typename V>
 class ResourceHashtableNode : public ResourceObj {
@@ -259,6 +261,26 @@ class ResourceHashtableBase : public STORAGE {
     }
   }
 
+  template<typename Function>
+  TableStatistics statistics_calculate(Function size_function) const {
+    NumberSeq summary;
+    size_t literal_bytes = 0;
+    Node* const* bucket = table();
+    const unsigned sz = table_size();
+    while (bucket < bucket_at(sz)) {
+      Node* node = *bucket;
+      int count = 0;
+      while (node != NULL) {
+        literal_bytes += size_function(node->_key, node->_value);
+        count++;
+        node = node->_next;
+      }
+      summary.add((double)count);
+      ++bucket;
+    }
+    return TableStatistics(summary, literal_bytes, sizeof(Node*), sizeof(Node));
+  }
+
 };
 
 template<unsigned TABLE_SIZE, typename K, typename V>

src/hotspot/share/utilities/tableStatistics.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2022, 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
@@ -91,7 +91,7 @@ TableStatistics::TableStatistics() :
   _add_rate(0), _remove_rate(0) {
 }
 
-TableStatistics::TableStatistics(TableRateStatistics& rate_stats, NumberSeq summary, size_t literal_bytes, size_t bucket_bytes, size_t node_bytes) :
+TableStatistics::TableStatistics(NumberSeq summary, size_t literal_bytes, size_t bucket_bytes, size_t node_bytes) :
   _literal_bytes(literal_bytes),
   _number_of_buckets(0), _number_of_entries(0),
   _maximum_bucket_size(0), _average_bucket_size(0),
@@ -114,7 +114,12 @@ TableStatistics::TableStatistics(TableRateStatistics& rate_stats, NumberSeq summ
 
   _bucket_size = (_number_of_buckets <= 0) ? 0 : (_bucket_bytes / _number_of_buckets);
   _entry_size = (_number_of_entries <= 0) ? 0 : (_entry_bytes / _number_of_entries);
+}
 
+TableStatistics::TableStatistics(TableRateStatistics& rate_stats,
+                                  NumberSeq summary, size_t literal_bytes,
+                                  size_t bucket_bytes, size_t node_bytes) :
+  TableStatistics(summary, literal_bytes, bucket_bytes, node_bytes) {
 #if INCLUDE_JFR
   if (Jfr::is_recording()) {
     rate_stats.stamp();

src/hotspot/share/utilities/tableStatistics.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2022, 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
@@ -82,6 +82,7 @@ public:
   float _remove_rate;
 
   TableStatistics();
+  TableStatistics(NumberSeq summary, size_t literal_bytes, size_t bucket_bytes, size_t node_bytes);
   TableStatistics(TableRateStatistics& rate_stats, NumberSeq summary, size_t literal_bytes, size_t bucket_bytes, size_t node_bytes);
   ~TableStatistics();
 

test/hotspot/gtest/utilities/test_resourceHash.cpp

@@ -446,3 +446,46 @@ TEST_VM_F(ResourceHashtableDeleteTest, check_delete_ptr) {
   // Removal should make the refcount be the original refcount.
   ASSERT_EQ(s->refcount(), s_orig_count) << "refcount should be as we started";
 }
+
+class ResourceHashtablePrintTest : public ::testing::Test {
+ public:
+    class TestValue {
+      int _i;
+      int _j;
+      int _k;
+     public:
+      TestValue(int i) : _i(i), _j(i+1), _k(i+2) {}
+    };
+    ResourceHashtable<int, TestValue*, 30, ResourceObj::C_HEAP, mtTest> _test_table;
+
+    class TableDeleter {
+     public:
+      bool do_entry(int& key, TestValue*& val) {
+        delete val;
+        return true;
+      }
+    };
+};
+
+TEST_VM_F(ResourceHashtablePrintTest, print_test) {
+  for (int i = 0; i < 300; i++) {
+    TestValue* tv = new TestValue(i);
+    _test_table.put(i, tv);  // all the entries can be the same.
+  }
+  auto printer = [&] (int& key, TestValue*& val) {
+    return sizeof(*val);
+  };
+  TableStatistics ts = _test_table.statistics_calculate(printer);
+  ResourceMark rm;
+  stringStream st;
+  ts.print(&st, "TestTable");
+  // Verify output in string
+  const char* strings[] = {
+      "Number of buckets", "Number of entries", "300", "Number of literals", "Average bucket size", "Maximum bucket size" };
+  for (const auto& str : strings) {
+    ASSERT_TRUE(strstr(st.as_string(), str) != nullptr) << "string not present " << str;
+  }
+  // Cleanup: need to delete pointers in entries
+  TableDeleter deleter;
+  _test_table.unlink(&deleter);
+}