Remove ReusableSetPool.

15 files changed, 0 insertions, 439 deletions

diff --git a/searchlib/src/vespa/searchlib/tensor/CMakeLists.txt b/searchlib/src/vespa/searchlib/tensor/CMakeLists.txt
index 0d87881711c..d1b88a7e2ab 100644
--- a/searchlib/src/vespa/searchlib/tensor/CMakeLists.txt
+++ b/searchlib/src/vespa/searchlib/tensor/CMakeLists.txt
@@ -35,6 +35,5 @@ vespa_add_library(searchlib_tensor OBJECT
     tensor_deserialize.cpp
     tensor_store.cpp
     tensor_store_saver.cpp
-    reusable_set_visited_tracker.cpp
     DEPENDS
 )
diff --git a/searchlib/src/vespa/searchlib/tensor/hnsw_index.cpp b/searchlib/src/vespa/searchlib/tensor/hnsw_index.cpp
index 10f06a1e1ec..a10ff1c48dc 100644
--- a/searchlib/src/vespa/searchlib/tensor/hnsw_index.cpp
+++ b/searchlib/src/vespa/searchlib/tensor/hnsw_index.cpp
@@ -23,8 +23,6 @@
 
 LOG_SETUP(".searchlib.tensor.hnsw_index");
 
-#define USE_OLD_VISITED_TRACKER 0
-
 namespace search::tensor {
 
 using search::AddressSpaceComponents;
@@ -319,15 +317,11 @@ HnswIndex::search_layer(const TypedCells& input, uint32_t neighbors_to_find,
         doc_id_limit = std::min(filter->size(), doc_id_limit);
     }
     uint32_t estimated_visited_nodes = estimate_visited_nodes(level, doc_id_limit, neighbors_to_find, filter);
-#if ! USE_OLD_VISITED_TRACKER
     if (estimated_visited_nodes >= doc_id_limit / 128) {
         search_layer_helper<BitVectorVisitedTracker>(input, neighbors_to_find, best_neighbors, level, filter, doc_id_limit, estimated_visited_nodes);
     } else {
         search_layer_helper<HashSetVisitedTracker>(input, neighbors_to_find, best_neighbors, level, filter, doc_id_limit, estimated_visited_nodes);
     }
-#else
-    search_layer_helper<ReusableSetVisitedTracker>(input, neighbors_to_find, best_neighbors, level, filter, doc_id_limit, estimated_visited_nodes);
-#endif
 }
 
 HnswIndex::HnswIndex(const DocVectorAccess& vectors, DistanceFunction::UP distance_func,
@@ -337,7 +331,6 @@ HnswIndex::HnswIndex(const DocVectorAccess& vectors, DistanceFunction::UP distan
       _distance_func(std::move(distance_func)),
       _level_generator(std::move(level_generator)),
       _cfg(cfg),
-      _visited_set_pool(),
       _compaction_spec()
 {
     assert(_distance_func);
@@ -597,7 +590,6 @@ HnswIndex::update_stat(const CompactionStrategy& compaction_strategy)
     _compaction_spec = HnswIndexCompactionSpec(compaction_strategy.should_compact(level_arrays_memory_usage, level_arrays_address_space_usage),
                                                compaction_strategy.should_compact(link_arrays_memory_usage, link_arrays_address_space_usage));
     result.merge(link_arrays_memory_usage);
-    result.merge(_visited_set_pool.memory_usage());
     return result;
 }
 
@@ -608,7 +600,6 @@ HnswIndex::memory_usage() const
     result.merge(_graph.node_refs.getMemoryUsage());
     result.merge(_graph.nodes.getMemoryUsage());
     result.merge(_graph.links.getMemoryUsage());
-    result.merge(_visited_set_pool.memory_usage());
     return result;
 }
 
@@ -628,10 +619,6 @@ HnswIndex::get_state(const vespalib::slime::Inserter& inserter) const
     StateExplorerUtils::memory_usage_to_slime(_graph.node_refs.getMemoryUsage(), memUsageObj.setObject("node_refs"));
     StateExplorerUtils::memory_usage_to_slime(_graph.nodes.getMemoryUsage(), memUsageObj.setObject("nodes"));
     StateExplorerUtils::memory_usage_to_slime(_graph.links.getMemoryUsage(), memUsageObj.setObject("links"));
-    StateExplorerUtils::memory_usage_to_slime(_visited_set_pool.memory_usage(), memUsageObj.setObject("visited_set_pool"));
-    auto& visitedObj = object.setObject("visited_set");
-    visitedObj.setLong("create_count", _visited_set_pool.create_count());
-    visitedObj.setLong("reuse_count", _visited_set_pool.reuse_count());
     object.setLong("nodes", _graph.size());
     auto& histogram_array = object.setArray("level_histogram");
     auto& links_hst_array = object.setArray("level_0_links_histogram");
diff --git a/searchlib/src/vespa/searchlib/tensor/hnsw_index.h b/searchlib/src/vespa/searchlib/tensor/hnsw_index.h
index 8a7422907ea..43e3001b496 100644
--- a/searchlib/src/vespa/searchlib/tensor/hnsw_index.h
+++ b/searchlib/src/vespa/searchlib/tensor/hnsw_index.h
@@ -15,7 +15,6 @@
 #include <vespa/vespalib/datastore/atomic_entry_ref.h>
 #include <vespa/vespalib/datastore/compaction_spec.h>
 #include <vespa/vespalib/datastore/entryref.h>
-#include <vespa/vespalib/util/reusable_set_pool.h>
 #include <vespa/vespalib/stllike/allocator.h>
 
 namespace search::tensor {
@@ -98,7 +97,6 @@ protected:
     DistanceFunction::UP _distance_func;
     RandomLevelGenerator::UP _level_generator;
     Config _cfg;
-    mutable vespalib::ReusableSetPool _visited_set_pool;
     HnswIndexCompactionSpec _compaction_spec;
 
     uint32_t max_links_for_level(uint32_t level) const;
@@ -221,7 +219,6 @@ public:
     bool check_link_symmetry() const;
     std::pair<uint32_t, bool> count_reachable_nodes() const;
     HnswGraph& get_graph() { return _graph; }
-    vespalib::ReusableSetPool& get_visited_set_pool() const noexcept { return _visited_set_pool; }
 
     static vespalib::datastore::ArrayStoreConfig make_default_node_store_config();
     static vespalib::datastore::ArrayStoreConfig make_default_link_store_config();
diff --git a/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.cpp b/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.cpp
deleted file mode 100644
index d3cdd28fea3..00000000000
--- a/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.cpp
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include "reusable_set_visited_tracker.h"
-#include "hnsw_index.h"
-
-namespace search::tensor {
-
-ReusableSetVisitedTracker::ReusableSetVisitedTracker(const HnswIndex& index, uint32_t doc_id_limit, uint32_t)
-    : _visited(index.get_visited_set_pool().get(doc_id_limit))
-{
-}
-
-ReusableSetVisitedTracker::~ReusableSetVisitedTracker() = default;
-
-}
diff --git a/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.h b/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.h
deleted file mode 100644
index 9528cfe78f9..00000000000
--- a/searchlib/src/vespa/searchlib/tensor/reusable_set_visited_tracker.h
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#pragma once
-
-#include <vespa/vespalib/util/reusable_set_handle.h>
-
-namespace search::tensor {
-
-class HnswIndex;
-
-/*
- * Tracker for visited nodes based on vespalib::ReusableSet.
- */
-class ReusableSetVisitedTracker
-{
-    vespalib::ReusableSetHandle _visited;
-public:
-    ReusableSetVisitedTracker(const HnswIndex& index, uint32_t doc_id_limit, uint32_t);
-    ~ReusableSetVisitedTracker();
-    void mark(uint32_t doc_id) { _visited.mark(doc_id); }
-    bool try_mark(uint32_t doc_id) {
-        if (_visited.is_marked(doc_id)) {
-            return false;
-        } else {
-            _visited.mark(doc_id);
-            return true;
-        }
-    }
-};
-
-}
diff --git a/vespalib/CMakeLists.txt b/vespalib/CMakeLists.txt
index 94ee05930d5..c498639533f 100644
--- a/vespalib/CMakeLists.txt
+++ b/vespalib/CMakeLists.txt
@@ -192,7 +192,6 @@ vespa_define_module(
     src/tests/util/mmap_file_allocator
     src/tests/util/mmap_file_allocator_factory
     src/tests/util/rcuvector
-    src/tests/util/reusable_set
     src/tests/util/size_literals
     src/tests/util/string_escape
     src/tests/valgrind
diff --git a/vespalib/src/tests/util/reusable_set/CMakeLists.txt b/vespalib/src/tests/util/reusable_set/CMakeLists.txt
deleted file mode 100644
index fa67311db6f..00000000000
--- a/vespalib/src/tests/util/reusable_set/CMakeLists.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-# Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-vespa_add_executable(vespalib_reusable_set_test_app TEST
-    SOURCES
-    reusable_set_test.cpp
-    DEPENDS
-    vespalib
-    GTest::GTest
-)
-vespa_add_test(NAME vespalib_reusable_set_test_app COMMAND vespalib_reusable_set_test_app)
diff --git a/vespalib/src/tests/util/reusable_set/reusable_set_test.cpp b/vespalib/src/tests/util/reusable_set/reusable_set_test.cpp
deleted file mode 100644
index fb3e73d03ed..00000000000
--- a/vespalib/src/tests/util/reusable_set/reusable_set_test.cpp
+++ /dev/null
@@ -1,139 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include <vespa/vespalib/util/reusable_set_pool.h>
-#include <vespa/vespalib/gtest/gtest.h>
-
-using namespace vespalib;
-
-using Mark = ReusableSet::Mark;
-
-void verify_set(const ReusableSet &set, size_t sz, Mark val, size_t marked) {
-    EXPECT_EQ(sz, set.capacity());
-    EXPECT_EQ(val, set.generation());
-    size_t count = 0;
-    for (size_t i = 0; i < set.capacity(); ++i) {
-        if (set.is_marked(i)) ++count;
-    }
-    EXPECT_EQ(marked, count);
-}
-
-void verify_handle(const ReusableSetHandle &set, size_t sz, Mark val, size_t marked) {
-    EXPECT_EQ(sz, set.capacity());
-    EXPECT_EQ(val, set.generation());
-    size_t count = 0;
-    for (size_t i = 0; i < set.capacity(); ++i) {
-        if (set.is_marked(i)) ++count;
-    }
-    EXPECT_EQ(marked, count);
-}
-
-class Pool : public ::testing::Test {
-public:
-    ReusableSetPool pool;
-    Pool() : pool() {}
-    ~Pool() {}
-    void exercise(ReusableSetHandle &set) {
-        size_t sz = set.capacity();
-        size_t count = 0;
-        for (size_t i = 0; i < sz; ++i) {
-            if (set.is_marked(i)) ++count;
-        }
-        EXPECT_EQ(0, count);
-        for (int i = 0; i < 17; ++i) {
-            set.mark((i * 711) % sz);
-        }
-        count = 0;
-        for (size_t i = 0; i < sz; ++i) {
-            if (set.is_marked(i)) ++count;
-        }
-        EXPECT_EQ(17, count);
-        for (int i = 0; i < 17; ++i) {
-            set.mark((i * 711) % sz);
-        }
-        count = 0;
-        for (size_t i = 0; i < sz; ++i) {
-            if (set.is_marked(i)) ++count;
-        }
-        EXPECT_EQ(17, count);
-   }
-};
-
-
-TEST(ReusableSetTest, simple_usage)
-{
-    ReusableSet visited(7);
-    verify_set(visited, 7, 1, 0);
-    visited.mark(1);
-    visited.mark(2);
-    visited.mark(4);
-    EXPECT_EQ(false, visited.is_marked(0));
-    EXPECT_EQ(true, visited.is_marked(1));
-    EXPECT_EQ(true, visited.is_marked(2));
-    EXPECT_EQ(false, visited.is_marked(3));
-    verify_set(visited, 7, 1, 3);
-    visited.mark(4);
-    visited.mark(1);
-    visited.mark(2);
-    verify_set(visited, 7, 1, 3);
-    EXPECT_EQ(false, visited.is_marked(0));
-    EXPECT_EQ(true, visited.is_marked(1));
-    EXPECT_EQ(true, visited.is_marked(2));
-    EXPECT_EQ(false, visited.is_marked(3));
-    visited.clear();
-    verify_set(visited, 7, 2, 0);
-    visited.clear();
-    verify_set(visited, 7, 3, 0);
-}
-
-TEST_F(Pool, reuse_works)
-{
-    for (int i = 0; i < 65535; ++i) {
-        auto handle = pool.get(7);
-        EXPECT_EQ(i, pool.reuse_count());
-        EXPECT_EQ(1, pool.create_count());
-        verify_handle(handle, 248, i+1, 0);
-        exercise(handle);
-    }
-    EXPECT_LT(500, pool.memory_usage().allocatedBytes());
-    EXPECT_GT(1000, pool.memory_usage().allocatedBytes());
-    for (int i = 0; i < 5; ++i) {
-        auto handle = pool.get(7);
-        EXPECT_EQ(65535+i, pool.reuse_count());
-        EXPECT_EQ(1, pool.create_count());
-        verify_handle(handle, 248, i+1, 0);
-        exercise(handle);
-    }
-    auto handle3 = pool.get(260);
-    EXPECT_EQ(2, pool.create_count());
-    verify_handle(handle3, 297, 1, 0);
-    exercise(handle3);
-    {
-        auto handle4 = pool.get(400);
-        EXPECT_EQ(3, pool.create_count());
-        verify_handle(handle4, 400, 1, 0);
-        exercise(handle4);
-        EXPECT_LT(1000, pool.memory_usage().usedBytes());
-        EXPECT_GT(2000, pool.memory_usage().usedBytes());
-    }
-    EXPECT_LT(500, pool.memory_usage().usedBytes());
-    EXPECT_GT(1000, pool.memory_usage().usedBytes());
-    auto handle7 = pool.get(401);
-    EXPECT_EQ(4, pool.create_count());
-    verify_handle(handle7, 480, 1, 0);
-    exercise(handle7);
-    EXPECT_LT(1000, pool.memory_usage().allocatedBytes());
-    EXPECT_GT(3000, pool.memory_usage().allocatedBytes());
-    {
-        auto handle8 = pool.get(2500);
-        auto handle9 = pool.get(2500);
-        EXPECT_LT(11000, pool.memory_usage().allocatedBytes());
-        EXPECT_GT(13000, pool.memory_usage().allocatedBytes());
-        auto handleA = pool.get(25000);
-        auto handleB = pool.get(25000);
-        EXPECT_LT(111000, pool.memory_usage().usedBytes());
-        EXPECT_GT(113000, pool.memory_usage().usedBytes());
-    }
-    EXPECT_GT(3000, pool.memory_usage().usedBytes());
-}
-
-GTEST_MAIN_RUN_ALL_TESTS()
diff --git a/vespalib/src/vespa/vespalib/util/CMakeLists.txt b/vespalib/src/vespa/vespalib/util/CMakeLists.txt
index 8cdc9444daa..3812fda4bdf 100644
--- a/vespalib/src/vespa/vespalib/util/CMakeLists.txt
+++ b/vespalib/src/vespa/vespalib/util/CMakeLists.txt
@@ -68,9 +68,6 @@ vespa_add_library(vespalib_vespalib_util OBJECT
     regexp.cpp
     require.cpp
     resource_limits.cpp
-    reusable_set.cpp
-    reusable_set_handle.cpp
-    reusable_set_pool.cpp
     round_up_to_page_size.cpp
     runnable.cpp
     runnable_pair.cpp
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set.cpp b/vespalib/src/vespa/vespalib/util/reusable_set.cpp
deleted file mode 100644
index 22b8903ccc7..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include "reusable_set.h"
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set.h b/vespalib/src/vespa/vespalib/util/reusable_set.h
deleted file mode 100644
index 081cad05df3..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set.h
+++ /dev/null
@@ -1,67 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#pragma once
-
-#include "array.h"
-#include "array.hpp"
-#include <memory>
-#include <cstring>
-
-
-namespace vespalib {
-
-/**
- * Generational marker implementation of a vector of boolean values.
- * Limited API, used for marking "seen" nodes when exploring a graph.
- **/
-class ReusableSet
-
-{
-public:
-    using Mark = unsigned short;
-
-    explicit ReusableSet(size_t size)
-      : _array(size),
-        _curval(-1),
-        _sz(size)
-    {
-        clear();
-    }
-
-    ~ReusableSet() {
-    }
-
-    /**
-     * Increments the generation value, only
-     * initializing the underlying memory when it wraps
-     **/
-    void clear() {
-        if (++_curval == 0) {
-            memset(bits(), 0, _sz * sizeof(Mark));
-            ++_curval;
-        }
-    }
-
-    void mark(size_t id) {
-        _array[id] = _curval;
-    }
-
-    bool is_marked(size_t id) const {
-        return (_array[id] == _curval);
-    }
-
-    Mark *bits() { return _array.begin(); }
-    Mark generation() const { return _curval; }
-    size_t capacity() const { return _sz; }
-
-    size_t memory_usage() const {
-        return (_sz * sizeof(Mark)) + sizeof(ReusableSet);
-    }
-
-private:
-    Array<Mark> _array;
-    Mark _curval;
-    size_t _sz;
-};
-
-} // namespace
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set_handle.cpp b/vespalib/src/vespa/vespalib/util/reusable_set_handle.cpp
deleted file mode 100644
index e7d5aef0eda..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set_handle.cpp
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include "reusable_set_handle.h"
-#include "reusable_set_pool.h"
-
-namespace vespalib {
-
-ReusableSetHandle::~ReusableSetHandle()
-{
-    _pool.reuse(std::move(_owned));
-}
-
-} // namespace
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set_handle.h b/vespalib/src/vespa/vespalib/util/reusable_set_handle.h
deleted file mode 100644
index 77a2e3a69d5..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set_handle.h
+++ /dev/null
@@ -1,52 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#pragma once
-
-#include "reusable_set.h"
-
-namespace vespalib {
-
-class ReusableSetPool;
-
-/**
- * Wraps a ReusableSet allocated from a ReusableSetPool.
- * Note that the handle returns the wrapped set to the pool
- * on destruction.
- **/
-class ReusableSetHandle
-{
-private:
-    using Mark = ReusableSet::Mark;
-    using RSUP = std::unique_ptr<ReusableSet>;
-
-    Mark *_bits;
-    Mark _curval;
-    RSUP _owned;
-    ReusableSetPool &_pool;
-
-public:
-    ReusableSetHandle(RSUP backing, ReusableSetPool& owner)
-      : _bits(backing->bits()),
-        _curval(backing->generation()),
-        _owned(std::move(backing)),
-        _pool(owner)
-    {}
-
-    ~ReusableSetHandle();
-
-    /** mark an ID */
-    void mark(size_t id) {
-        _bits[id] = _curval;
-    }
-
-    /** check if an ID has been marked */
-    bool is_marked(size_t id) const {
-        return (_bits[id] == _curval);
-    }
-
-    // for unit tests and statistics
-    size_t capacity() const { return _owned->capacity(); }
-    Mark generation() const { return _curval; }
-};
-
-} // namespace
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set_pool.cpp b/vespalib/src/vespa/vespalib/util/reusable_set_pool.cpp
deleted file mode 100644
index c59c2220457..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set_pool.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#include "reusable_set_pool.h"
diff --git a/vespalib/src/vespa/vespalib/util/reusable_set_pool.h b/vespalib/src/vespa/vespalib/util/reusable_set_pool.h
deleted file mode 100644
index 65a0630f4ac..00000000000
--- a/vespalib/src/vespa/vespalib/util/reusable_set_pool.h
+++ /dev/null
@@ -1,86 +0,0 @@
-// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-#pragma once
-
-#include "reusable_set.h"
-#include "reusable_set_handle.h"
-#include "memoryusage.h"
-
-#include <vector>
-#include <mutex>
-
-namespace vespalib {
-
-/**
- * A resource pool for ReusableSet instances.
- * Note that the pool should have a guaranteed lifetime
- * that is longer than any Handle retrieved from the pool.
- **/
-class ReusableSetPool
-{
-    using RSUP = std::unique_ptr<ReusableSet>;
-    using Guard = std::lock_guard<std::mutex>;
-    std::vector<RSUP> _lru_stack;
-    mutable std::mutex _lock;
-    size_t _reuse_count;
-    size_t _create_count;
-    MemoryUsage _total_memory;
-    const size_t _min_size;
-    const size_t _grow_percent;
-
-    ReusableSetPool(const ReusableSetPool &) = delete;
-    ReusableSetPool& operator= (const ReusableSetPool &) = delete;
-
-public:
-    ReusableSetPool()
-      : _lru_stack(), _lock(),
-        _reuse_count(0), _create_count(0),
-        _total_memory(),
-        _min_size(248), _grow_percent(20)
-    {
-        _total_memory.incAllocatedBytes(sizeof(ReusableSetPool));
-    }
-
-    /** Create or re-use a set with (at least) the given size. */
-    ReusableSetHandle get(size_t size) {
-        Guard guard(_lock);
-        size_t last_used_size = 0;
-        while (! _lru_stack.empty()) {
-            RSUP r = std::move(_lru_stack.back());
-            _lru_stack.pop_back();
-            if (r->capacity() >= size) {
-                r->clear();
-                ++_reuse_count;
-                _total_memory.incUsedBytes(r->memory_usage());
-                return ReusableSetHandle(std::move(r), *this);
-            }
-            _total_memory.decAllocatedBytes(r->memory_usage());
-            last_used_size = std::max(last_used_size, r->capacity());
-        }
-        double grow_factor = (1.0 + _grow_percent / 100.0);
-        last_used_size *= grow_factor;
-        size_t at_least_size = std::max(_min_size, last_used_size);
-        RSUP r = std::make_unique<ReusableSet>(std::max(at_least_size, size));
-        _total_memory.incAllocatedBytes(r->memory_usage());
-        ++_create_count;
-        _total_memory.incUsedBytes(r->memory_usage());
-        return ReusableSetHandle(std::move(r), *this);
-    }
-
-    /** Return a ReusableSet to the pool. */
-    void reuse(RSUP used) {
-        Guard guard(_lock);
-        _total_memory.decUsedBytes(used->memory_usage());
-        _lru_stack.push_back(std::move(used));
-    }
-
-    // for unit testing and statistics
-    size_t reuse_count() const { return _reuse_count; }
-    size_t create_count() const { return _create_count; }
-    MemoryUsage memory_usage() const {
-        Guard guard(_lock);
-        return _total_memory;
-    }
-};
-
-} // namespace