File: lru_cache_test.cc

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//  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 "util/testharness.h"

namespace rocksdb {

class LRUCacheTest : public testing::Test {
 public:
  LRUCacheTest() {}
  ~LRUCacheTest() { 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) {
    DeleteCache();
    cache_ = reinterpret_cast<LRUCacheShard*>(
        port::cacheline_aligned_alloc(sizeof(LRUCacheShard)));
    new (cache_) LRUCacheShard(capacity, false /*strict_capcity_limit*/,
                               high_pri_pool_ratio);
  }

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

}  // namespace rocksdb

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