add prioritized cache wrapper

CMakeLists.txt

@@ -100,7 +100,8 @@ if (WITH_TITAN_TESTS AND (NOT CMAKE_BUILD_TYPE STREQUAL "Release"))
         titan_db_test
         titan_options_test
         util_test
-        version_test)
+        version_test
+        prioritized_cache_test)
   set(TEST_LIBS
         titan
         rocksdb

include/titan/prioritized_cache.h

@@ -0,0 +1,117 @@
+#pragma once
+#include "rocksdb/cache.h"
+
+namespace rocksdb {
+namespace titandb {
+
+class PrioritizedCache : public Cache {
+ public:
+  // Constructs a PrioritizedCache, which is a wrapper
+  // of rocksdb Cache
+  PrioritizedCache(std::shared_ptr<Cache> cache, Cache::Priority priority);
+  ~PrioritizedCache();
+
+  // Get the Cache ptr
+  std::shared_ptr<Cache> GetCache();
+
+  // always insert into the cache with the priority when init,
+  // regardless of user provided option
+  Status Insert(const Slice& key, void* value, size_t charge,
+                void (*deleter)(const Slice& key, void* value),
+                Cache::Handle** handle, Cache::Priority /*priority*/) override;
+
+  // The type of the Cache
+  const char* Name() const override;
+
+  // If the cache has no mapping for "key", returns nullptr.
+  //
+  // Else return a handle that corresponds to the mapping.  The caller
+  // must call this->Release(handle) when the returned mapping is no
+  // longer needed.
+  // If stats is not nullptr, relative tickers could be used inside the
+  // function.
+  Cache::Handle* Lookup(const Slice& key, Statistics* stats = nullptr) override;
+
+  // Increments the reference count for the handle if it refers to an entry in
+  // the cache. Returns true if refcount was incremented; otherwise, returns
+  // false.
+  // REQUIRES: handle must have been returned by a method on *this.
+  bool Ref(Cache::Handle* handle) override;
+
+  /**
+   * Release a mapping returned by a previous Lookup(). A released entry might
+   * still  remain in cache in case it is later looked up by others. If
+   * force_erase is set then it also erase it from the cache if there is no
+   * other reference to  it. Erasing it should call the deleter function that
+   * was provided when the
+   * entry was inserted.
+   *
+   * Returns true if the entry was also erased.
+   */
+  // REQUIRES: handle must not have been released yet.
+  // REQUIRES: handle must have been returned by a method on *this.
+  bool Release(Cache::Handle* handle, bool force_erase = false) override;
+
+  // Return the value encapsulated in a handle returned by a
+  // successful Lookup().
+  // REQUIRES: handle must not have been released yet.
+  // REQUIRES: handle must have been returned by a method on *this.
+  void* Value(Cache::Handle* handle) override;
+
+  // If the cache contains entry for key, erase it.  Note that the
+  // underlying entry will be kept around until all existing handles
+  // to it have been released.
+  void Erase(const Slice& key) override;
+
+  // Return a new numeric id.  May be used by multiple clients who are
+  // sharding the same cache to partition the key space.  Typically the
+  // client will allocate a new id at startup and prepend the id to
+  // its cache keys.
+  uint64_t NewId() override;
+
+  // sets the maximum configured capacity of the cache. When the new
+  // capacity is less than the old capacity and the existing usage is
+  // greater than new capacity, the implementation will do its best job to
+  // purge the released entries from the cache in order to lower the usage
+  void SetCapacity(size_t capacity) override;
+
+  // Set whether to return error on insertion when cache reaches its full
+  // capacity.
+  void SetStrictCapacityLimit(bool strict_capacity_limit) override;
+
+  // Get the flag whether to return error on insertion when cache reaches its
+  // full capacity.
+  bool HasStrictCapacityLimit() const override;
+
+  // returns the maximum configured capacity of the cache
+  size_t GetCapacity() const override;
+
+  // returns the memory size for the entries residing in the cache.
+  size_t GetUsage() const override;
+
+  // returns the memory size for a specific entry in the cache.
+  size_t GetUsage(Cache::Handle* handle) const override;
+
+  // returns the memory size for the entries in use by the system
+  size_t GetPinnedUsage() const override;
+
+  // returns the charge for the specific entry in the cache.
+  size_t GetCharge(Cache::Handle* handle) const override;
+
+  // Apply callback to all entries in the cache
+  // If thread_safe is true, it will also lock the accesses. Otherwise, it will
+  // access the cache without the lock held
+  void ApplyToAllCacheEntries(void (*callback)(void*, size_t),
+                              bool thread_safe) override;
+
+  // Remove all entries.
+  // Prerequisite: no entry is referenced.
+  void EraseUnRefEntries() override;
+
+ private:
+  std::shared_ptr<Cache> cache_;
+  Cache::Priority priority_;
+};
+
+}  // namespace titandb
+}  // namespace rocksdb

src/prioritized_cache.cc

@@ -0,0 +1,78 @@
+#include "titan/prioritized_cache.h"
+
+namespace rocksdb {
+namespace titandb {
+
+PrioritizedCache::PrioritizedCache(std::shared_ptr<Cache> cache,
+                                   Cache::Priority priority)
+    : cache_(cache), priority_(priority) {}
+
+PrioritizedCache::~PrioritizedCache() {}
+
+std::shared_ptr<Cache> PrioritizedCache::GetCache() { return cache_; }
+
+Status PrioritizedCache::Insert(const Slice& key, void* value, size_t charge,
+                                void (*deleter)(const Slice& key, void* value),
+                                Cache::Handle** handle,
+                                Cache::Priority /*priority*/) {
+  return cache_->Insert(key, value, charge, deleter, handle, priority_);
+}
+
+const char* PrioritizedCache::Name() const { return "PrioritizedCache"; }
+
+Cache::Handle* PrioritizedCache::Lookup(const Slice& key,
+                                 Statistics* stats) {
+  return cache_->Lookup(key, stats);
+}
+
+bool PrioritizedCache::Ref(Cache::Handle* handle) { return cache_->Ref(handle); }
+
+bool PrioritizedCache::Release(Cache::Handle* handle, bool force_erase) {
+  return cache_->Release(handle, force_erase);
+}
+
+void* PrioritizedCache::Value(Cache::Handle* handle) { return cache_->Value(handle); }
+
+void PrioritizedCache::Erase(const Slice& key) { cache_->Erase(key); }
+
+uint64_t PrioritizedCache::NewId() { return cache_->NewId(); }
+
+void PrioritizedCache::SetCapacity(size_t capacity) {
+  cache_->SetCapacity(capacity);
+}
+
+void PrioritizedCache::SetStrictCapacityLimit(bool strict_capacity_limit) {
+  cache_->SetStrictCapacityLimit(strict_capacity_limit);
+}
+
+bool PrioritizedCache::HasStrictCapacityLimit() const {
+  return cache_->HasStrictCapacityLimit();
+}
+
+size_t PrioritizedCache::GetCapacity() const { return cache_->GetCapacity(); }
+
+size_t PrioritizedCache::GetUsage() const { return cache_->GetUsage(); }
+
+size_t PrioritizedCache::GetUsage(Cache::Handle* handle) const {
+  return cache_->GetUsage();
+}
+
+size_t PrioritizedCache::GetPinnedUsage() const {
+  return cache_->GetPinnedUsage();
+}
+
+size_t PrioritizedCache::GetCharge(Cache::Handle* handle) const {
+  return cache_->GetCharge(handle);
+}
+
+void PrioritizedCache::ApplyToAllCacheEntries(void (*callback)(void*, size_t),
+                                              bool thread_safe) {
+  return cache_->ApplyToAllCacheEntries(callback, thread_safe);
+}
+
+void PrioritizedCache::EraseUnRefEntries() {
+  return cache_->EraseUnRefEntries();
+}
+
+}  // namespace titandb
+}  // namespace rocksdb

src/prioritized_cache_test.cc

@@ -0,0 +1,61 @@
+#include "titan/prioritized_cache.h"
+#include "test_util/testharness.h"
+#include "util.h"
+
+namespace rocksdb {
+namespace titandb {
+
+class PrioritizedCacheTest : public testing::Test {
+public:
+  PrioritizedCacheTest() {}
+  ~PrioritizedCacheTest() {}
+};
+
+TEST_F(PrioritizedCacheTest, PriorityTest) {
+  Slice high_cache_key = "high_test_key";
+  Slice cacahe_value = "test_value";
+  Slice low_cache_key = "low_test_key";
+
+  LRUCacheOptions options;
+  options.capacity = high_cache_key.size() + cacahe_value.size();
+  options.high_pri_pool_ratio = 1;
+
+  std::shared_ptr<Cache> cache = NewLRUCache(options);
+  cache->SetCapacity(high_cache_key.size() + cacahe_value.size());
+  PrioritizedCache high_cache(cache, Cache::Priority::HIGH);
+  PrioritizedCache low_cache(cache, Cache::Priority::LOW);
+  Cache::Handle* cache_handle = cache->Lookup(high_cache_key);
+
+  // here we set insert Priority to high, to check if it will 
+  // insert to low in fact
+  auto lo_ok = low_cache.Insert(low_cache_key, (void*)&cacahe_value, cache->GetCapacity(), 
+      &DeleteCacheValue<Slice>, &cache_handle, Cache::Priority::LOW);
+  ASSERT_TRUE(lo_ok.ok());
+
+  // here we set insert Priority to low, to check if it will 
+  // insert to high in fact
+  auto hi_ok = high_cache.Insert(high_cache_key, (void*)&cacahe_value, cache->GetCapacity(), 
+      &DeleteCacheValue<Slice>, &cache_handle, Cache::Priority::LOW);
+  ASSERT_TRUE(hi_ok.ok());
+
+  auto high_handle = cache->Lookup(high_cache_key);
+  if (high_handle) {
+    auto v = reinterpret_cast<Slice*>(cache->Value(high_handle));
+    ASSERT_EQ(cacahe_value.data(), v->data());
+  }
+
+  auto low_handle = cache->Lookup(low_cache_key);
+  if (low_handle) {
+    auto v = reinterpret_cast<Slice*>(cache->Value(low_handle));
+    ASSERT_EQ(cacahe_value.data(), v->data());
+  }
+
+}
+
+}  // namespace titandb
+}  // namespace rocksdb
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}