rocksdb/cache/lru_cache_test.cc

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#include "cache/lru_cache.h"

#include <string>
#include <vector>

#include "port/port.h"
#include "rocksdb/cache.h"
#include "test_util/testharness.h"
#include "util/coding.h"
#include "util/random.h"

namespace ROCKSDB_NAMESPACE {

class LRUCacheTest : public testing::Test {
 public:
  LRUCacheTest() {}
  ~LRUCacheTest() override { DeleteCache(); }

  void DeleteCache() {
    if (cache_ != nullptr) {
      cache_->~LRUCacheShard();
      port::cacheline_aligned_free(cache_);
      cache_ = nullptr;
    }
  }

  void NewCache(size_t capacity, double high_pri_pool_ratio = 0.0,
                bool use_adaptive_mutex = kDefaultToAdaptiveMutex) {
    DeleteCache();
    cache_ = reinterpret_cast<LRUCacheShard*>(
        port::cacheline_aligned_alloc(sizeof(LRUCacheShard)));
    new (cache_) LRUCacheShard(capacity, false /*strict_capacity_limit*/,
                               high_pri_pool_ratio, use_adaptive_mutex,
                               kDontChargeCacheMetadata, nullptr /*nvm_cache*/);
  }

  void Insert(const std::string& key,
              Cache::Priority priority = Cache::Priority::LOW) {
    EXPECT_OK(cache_->Insert(key, 0 /*hash*/, nullptr /*value*/, 1 /*charge*/,
                             nullptr /*deleter*/, nullptr /*handle*/,
                             priority));
  }

  void Insert(char key, Cache::Priority priority = Cache::Priority::LOW) {
    Insert(std::string(1, key), priority);
  }

  bool Lookup(const std::string& key) {
    auto handle = cache_->Lookup(key, 0 /*hash*/);
    if (handle) {
      cache_->Release(handle);
      return true;
    }
    return false;
  }

  bool Lookup(char key) { return Lookup(std::string(1, key)); }

  void Erase(const std::string& key) { cache_->Erase(key, 0 /*hash*/); }

  void ValidateLRUList(std::vector<std::string> keys,
                       size_t num_high_pri_pool_keys = 0) {
    LRUHandle* lru;
    LRUHandle* lru_low_pri;
    cache_->TEST_GetLRUList(&lru, &lru_low_pri);
    LRUHandle* iter = lru;
    bool in_high_pri_pool = false;
    size_t high_pri_pool_keys = 0;
    if (iter == lru_low_pri) {
      in_high_pri_pool = true;
    }
    for (const auto& key : keys) {
      iter = iter->next;
      ASSERT_NE(lru, iter);
      ASSERT_EQ(key, iter->key().ToString());
      ASSERT_EQ(in_high_pri_pool, iter->InHighPriPool());
      if (in_high_pri_pool) {
        high_pri_pool_keys++;
      }
      if (iter == lru_low_pri) {
        ASSERT_FALSE(in_high_pri_pool);
        in_high_pri_pool = true;
      }
    }
    ASSERT_EQ(lru, iter->next);
    ASSERT_TRUE(in_high_pri_pool);
    ASSERT_EQ(num_high_pri_pool_keys, high_pri_pool_keys);
  }

 private:
  LRUCacheShard* cache_ = nullptr;
};

TEST_F(LRUCacheTest, BasicLRU) {
  NewCache(5);
  for (char ch = 'a'; ch <= 'e'; ch++) {
    Insert(ch);
  }
  ValidateLRUList({"a", "b", "c", "d", "e"});
  for (char ch = 'x'; ch <= 'z'; ch++) {
    Insert(ch);
  }
  ValidateLRUList({"d", "e", "x", "y", "z"});
  ASSERT_FALSE(Lookup("b"));
  ValidateLRUList({"d", "e", "x", "y", "z"});
  ASSERT_TRUE(Lookup("e"));
  ValidateLRUList({"d", "x", "y", "z", "e"});
  ASSERT_TRUE(Lookup("z"));
  ValidateLRUList({"d", "x", "y", "e", "z"});
  Erase("x");
  ValidateLRUList({"d", "y", "e", "z"});
  ASSERT_TRUE(Lookup("d"));
  ValidateLRUList({"y", "e", "z", "d"});
  Insert("u");
  ValidateLRUList({"y", "e", "z", "d", "u"});
  Insert("v");
  ValidateLRUList({"e", "z", "d", "u", "v"});
}

TEST_F(LRUCacheTest, MidpointInsertion) {
  // Allocate 2 cache entries to high-pri pool.
  NewCache(5, 0.45);

  Insert("a", Cache::Priority::LOW);
  Insert("b", Cache::Priority::LOW);
  Insert("c", Cache::Priority::LOW);
  Insert("x", Cache::Priority::HIGH);
  Insert("y", Cache::Priority::HIGH);
  ValidateLRUList({"a", "b", "c", "x", "y"}, 2);

  // Low-pri entries inserted to the tail of low-pri list (the midpoint).
  // After lookup, it will move to the tail of the full list.
  Insert("d", Cache::Priority::LOW);
  ValidateLRUList({"b", "c", "d", "x", "y"}, 2);
  ASSERT_TRUE(Lookup("d"));
  ValidateLRUList({"b", "c", "x", "y", "d"}, 2);

  // High-pri entries will be inserted to the tail of full list.
  Insert("z", Cache::Priority::HIGH);
  ValidateLRUList({"c", "x", "y", "d", "z"}, 2);
}

TEST_F(LRUCacheTest, EntriesWithPriority) {
  // Allocate 2 cache entries to high-pri pool.
  NewCache(5, 0.45);

  Insert("a", Cache::Priority::LOW);
  Insert("b", Cache::Priority::LOW);
  Insert("c", Cache::Priority::LOW);
  ValidateLRUList({"a", "b", "c"}, 0);

  // Low-pri entries can take high-pri pool capacity if available
  Insert("u", Cache::Priority::LOW);
  Insert("v", Cache::Priority::LOW);
  ValidateLRUList({"a", "b", "c", "u", "v"}, 0);

  Insert("X", Cache::Priority::HIGH);
  Insert("Y", Cache::Priority::HIGH);
  ValidateLRUList({"c", "u", "v", "X", "Y"}, 2);

  // High-pri entries can overflow to low-pri pool.
  Insert("Z", Cache::Priority::HIGH);
  ValidateLRUList({"u", "v", "X", "Y", "Z"}, 2);

  // Low-pri entries will be inserted to head of low-pri pool.
  Insert("a", Cache::Priority::LOW);
  ValidateLRUList({"v", "X", "a", "Y", "Z"}, 2);

  // Low-pri entries will be inserted to head of high-pri pool after lookup.
  ASSERT_TRUE(Lookup("v"));
  ValidateLRUList({"X", "a", "Y", "Z", "v"}, 2);

  // High-pri entries will be inserted to the head of the list after lookup.
  ASSERT_TRUE(Lookup("X"));
  ValidateLRUList({"a", "Y", "Z", "v", "X"}, 2);
  ASSERT_TRUE(Lookup("Z"));
  ValidateLRUList({"a", "Y", "v", "X", "Z"}, 2);

  Erase("Y");
  ValidateLRUList({"a", "v", "X", "Z"}, 2);
  Erase("X");
  ValidateLRUList({"a", "v", "Z"}, 1);
  Insert("d", Cache::Priority::LOW);
  Insert("e", Cache::Priority::LOW);
  ValidateLRUList({"a", "v", "d", "e", "Z"}, 1);
  Insert("f", Cache::Priority::LOW);
  Insert("g", Cache::Priority::LOW);
  ValidateLRUList({"d", "e", "f", "g", "Z"}, 1);
  ASSERT_TRUE(Lookup("d"));
  ValidateLRUList({"e", "f", "g", "Z", "d"}, 2);
}

class TestNvmCache : public NvmCache {
 public:
  TestNvmCache(size_t capacity) : num_inserts_(0), num_lookups_(0) {
    cache_ = NewLRUCache(capacity, 0, false, 0.5, nullptr,
                         kDefaultToAdaptiveMutex, kDontChargeCacheMetadata);
  }
  ~TestNvmCache() { cache_.reset(); }

  std::string Name() override { return "TestNvmCache"; }

  Status Insert(const Slice& key, void* value,
                Cache::CacheItemHelperCallback helper_cb) override {
    Cache::SizeCallback size_cb;
    Cache::SaveToCallback save_cb;
    size_t size;
    char* buf;
    Status s;

    num_inserts_++;
    (*helper_cb)(&size_cb, &save_cb, nullptr);
    size = (*size_cb)(value);
    buf = new char[size + sizeof(uint64_t)];
    EncodeFixed64(buf, size);
    s = (*save_cb)(value, 0, size, buf + sizeof(uint64_t));
    EXPECT_OK(s);
    return cache_->Insert(key, buf, size,
                          [](const Slice& /*key*/, void* val) -> void {
                            delete[] reinterpret_cast<char*>(val);
                          });
  }

  std::unique_ptr<NvmCacheHandle> Lookup(const Slice& key,
                                         const Cache::CreateCallback& create_cb,
                                         bool /*wait*/) override {
    std::unique_ptr<TestNvmCacheHandle> nvm_handle;
    Cache::Handle* handle = cache_->Lookup(key);
    num_lookups_++;
    if (handle) {
      void* value;
      size_t charge;
      char* ptr = (char*)cache_->Value(handle);
      size_t size = DecodeFixed64(ptr);
      ptr += sizeof(uint64_t);
      Status s = create_cb(ptr, size, &value, &charge);
      EXPECT_OK(s);
      nvm_handle.reset(
          new TestNvmCacheHandle(cache_.get(), handle, value, charge));
    }
    return nvm_handle;
  }

  void Erase(const Slice& /*key*/) override {}

  void WaitAll(std::vector<NvmCacheHandle*> /*handles*/) override {}

  std::string GetPrintableOptions() const override { return ""; }

  uint32_t num_inserts() { return num_inserts_; }

  uint32_t num_lookups() { return num_lookups_; }

 private:
  class TestNvmCacheHandle : public NvmCacheHandle {
   public:
    TestNvmCacheHandle(Cache* cache, Cache::Handle* handle, void* value,
                       size_t size)
        : cache_(cache), handle_(handle), value_(value), size_(size) {}
    ~TestNvmCacheHandle() {
      cache_->Release(handle_);
    }

    bool isReady() override { return true; }

    void Wait() override {}

    void* Value() override { return value_; }

    size_t Size() override { return size_; }

   private:
    Cache* cache_;
    Cache::Handle* handle_;
    void* value_;
    size_t size_;
  };

  std::shared_ptr<Cache> cache_;
  uint32_t num_inserts_;
  uint32_t num_lookups_;
};

TEST_F(LRUCacheTest, TestNvmCache) {
  LRUCacheOptions opts(1024, 0, false, 0.5, nullptr, kDefaultToAdaptiveMutex,
                       kDontChargeCacheMetadata);
  std::shared_ptr<TestNvmCache> nvm_cache(new TestNvmCache(2048));
  opts.nvm_cache = nvm_cache;
  std::shared_ptr<Cache> cache = NewLRUCache(opts);

  class TestItem {
   public:
    TestItem(const char* buf, size_t size) : buf_(new char[size]), size_(size) {
      memcpy(buf_.get(), buf, size);
    }
    ~TestItem() {}

    char* Buf() { return buf_.get(); }
    size_t Size() { return size_; }

   private:
    std::unique_ptr<char[]> buf_;
    size_t size_;
  };

  Cache::CacheItemHelperCallback helper_cb =
      [](Cache::SizeCallback* size_cb, Cache::SaveToCallback* saveto_cb,
         Cache::DeletionCallback* del_cb) -> void {
    if (size_cb) {
      *size_cb = [](void* obj) -> size_t {
        return reinterpret_cast<TestItem*>(obj)->Size();
      };
    }
    if (saveto_cb) {
      *saveto_cb = [](void* obj, size_t offset, size_t size,
                      void* out) -> Status {
        TestItem* item = reinterpret_cast<TestItem*>(obj);
        char* buf = item->Buf();
        EXPECT_EQ(size, item->Size());
        EXPECT_EQ(offset, 0);
        memcpy(out, buf, size);
        return Status::OK();
      };
    }
    if (del_cb) {
      *del_cb = [](const Slice& /*key*/, void* obj) -> void {
        delete reinterpret_cast<TestItem*>(obj);
      };
    }
  };

  int create_count = 0;
  Cache::CreateCallback test_item_creator =
      [&create_count](void* buf, size_t size, void** out_obj,
                      size_t* charge) -> Status {
    create_count++;
    *out_obj = reinterpret_cast<void*>(new TestItem((char*)buf, size));
    *charge = size;
    return Status::OK();
  };

  Random rnd(301);
  std::string str1 = rnd.RandomString(1020);
  TestItem* item1 = new TestItem(str1.data(), str1.length());
  cache->Insert("k1", item1, helper_cb, str1.length());
  std::string str2 = rnd.RandomString(1020);
  TestItem* item2 = new TestItem(str2.data(), str2.length());
  // k2 should be demoted to NVM
  cache->Insert("k2", item2, helper_cb, str2.length());

  Cache::Handle* handle;
  handle = cache->Lookup("k2", helper_cb, test_item_creator,
                         Cache::Priority::LOW, true);
  ASSERT_NE(handle, nullptr);
  cache->Release(handle);
  // This lookup should promote k1 and demote k2
  handle = cache->Lookup("k1", helper_cb, test_item_creator,
                         Cache::Priority::LOW, true);
  ASSERT_NE(handle, nullptr);
  cache->Release(handle);
  ASSERT_EQ(nvm_cache->num_inserts(), 2);
  ASSERT_EQ(nvm_cache->num_lookups(), 1);
}
}  // namespace ROCKSDB_NAMESPACE

int main(int argc, char** argv) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}