Feat(common): optimize cache promotion and demotion

Signed-off-by: zztaki <[email protected]>

Author: zztaki

src/common/lru_cache.h

@@ -204,7 +204,7 @@ class LRUCache : public LRUCacheInterface<K, V> {
     void Remove(const K &key) override;
 
     /*
-    * @brief Get the first key that $value = value
+    * @brief Get the first key that $value = value from lru tail to head
     *
     * @param[in] value
     * @param[out] key
@@ -429,10 +429,7 @@ void LRUCache<K, V, KeyTraits, ValueTraits>::RemoveLocked(const K &key) {
 template <typename K,  typename V, typename KeyTraits, typename ValueTraits>
 void LRUCache<K, V, KeyTraits, ValueTraits>::MoveToFront(
     const typename std::list<Item>::iterator &elem) {
-    Item duplica{elem->key, elem->value};
-    ll_.erase(elem);
-    ll_.push_front(duplica);
-    cache_[*(duplica.key)] = ll_.begin();
+    ll_.splice(ll_.begin(), ll_, elem);
 }
 
 template <typename K,  typename V, typename KeyTraits, typename ValueTraits>
@@ -699,16 +696,8 @@ bool SglLRUCache<K, KeyTraits>::MoveBack(const K &key) {
     if (iter == cache_.end()) {
         return false;
     }
-    // delete the old value
-    RemoveElement(iter->second);
-    // put new value at tail
-    ll_.push_back(key);
-    cache_[key] = --ll_.end();
-    size_++;
-    if (cacheMetrics_ != nullptr) {
-        cacheMetrics_->UpdateAddToCacheCount();
-        cacheMetrics_->UpdateAddToCacheBytes(KeyTraits::CountBytes(key));
-    }
+    // move key to list tail
+    ll_.splice(ll_.end(), ll_, iter->second);
     return true;
 }
 
@@ -806,10 +795,7 @@ void SglLRUCache<K, KeyTraits>::RemoveLocked(const K &key) {
 template <typename K, typename KeyTraits>
 void SglLRUCache<K, KeyTraits>::MoveToFront(
     const typename std::list<K>::iterator &elem) {
-    K tmp = *elem;
-    ll_.erase(elem);
-    ll_.emplace_front(tmp);
-    cache_[tmp] = ll_.begin();
+    ll_.splice(ll_.begin(), ll_, elem);
 }
 
 template <typename K, typename KeyTraits>

test/common/lru_cache_test.cpp

@@ -212,6 +212,51 @@ TEST(CaCheTest, TestCacheGetLastKVWithFunction) {
     ASSERT_EQ(false, ok);
 }
 
+TEST(CaCheTest, TestCachePromotion) {
+    auto cache = std::make_shared<LRUCache<int, int>>(
+        std::make_shared<CacheMetrics>("LruCache"));
+
+    int k, v;
+    for (int k = 0; k < 5; k++) {
+        v = k;
+        cache->Put(k, v);
+    }
+    // now cache list: 4 3 2 1 0
+
+    for (int k = 0; k < 5; k += 2) {
+        cache->Get(k, &v);
+        ASSERT_EQ(k, v);
+    }
+    // now cache list: 4 2 0 3 1
+
+    cache->GetLast(&k, &v);
+    cache->Remove(k);;
+    ASSERT_EQ(1, k);
+    ASSERT_EQ(1, v);
+
+    cache->GetLast(&k, &v);
+    cache->Remove(k);;
+    ASSERT_EQ(3, k);
+    ASSERT_EQ(3, v);
+
+    cache->GetLast(&k, &v);
+    cache->Remove(k);;
+    ASSERT_EQ(0, k);
+    ASSERT_EQ(0, v);
+
+    cache->GetLast(&k, &v);
+    cache->Remove(k);;
+    ASSERT_EQ(2, k);
+    ASSERT_EQ(2, v);
+
+    cache->GetLast(&k, &v);
+    cache->Remove(k);;
+    ASSERT_EQ(4, k);
+    ASSERT_EQ(4, v);
+
+    ASSERT_EQ(0, cache->GetCacheMetrics()->cacheCount.get_value());
+}
+
 TEST(SglCaCheTest, TestGetBefore) {
     auto cache = std::make_shared<SglLRUCache<int>>(
         std::make_shared<CacheMetrics>("LruCache"));
@@ -302,6 +347,83 @@ TEST(SglCaCheTest, TestCacheHitAndMissMetric) {
     ASSERT_EQ(10, cache->GetCacheMetrics()->cacheMiss.get_value());
 }
 
+TEST(SglCaCheTest, TestCachePromotionAndDemotion) {
+    auto cache = std::make_shared<SglLRUCache<int>>(
+        std::make_shared<CacheMetrics>("LruCache"));
+
+    // test promotion
+    {
+        int k;
+        for (int k = 0; k < 5; k++) {
+            cache->Put(k);
+        }
+        // now cache list: 4 3 2 1 0
+
+        for (int k = 0; k < 5; k += 2) {
+            ASSERT_EQ(cache->IsCached(k), true);
+        }
+        // now cache list: 4 2 0 3 1
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(1, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(3, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(0, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(2, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(4, k);
+
+        ASSERT_EQ(0, cache->GetCacheMetrics()->cacheCount.get_value());
+    }
+
+    // test demotion
+    {
+        int k;
+        for (int k = 0; k < 5; k++) {
+            cache->Put(k);
+        }
+        // now cache list: 4 3 2 1 0
+
+        for (int k = 4; k >= 0; k -= 2) {
+            ASSERT_EQ(cache->MoveBack(k), true);
+        }
+        // now cache list: 3 1 4 2 0
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(0, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(2, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(4, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(1, k);
+
+        cache->GetBack(&k);
+        cache->Remove(k);;
+        ASSERT_EQ(3, k);
+
+        ASSERT_EQ(0, cache->GetCacheMetrics()->cacheCount.get_value());
+    }
+}
+
 TEST(TimedCaCheTest, test_base) {
     int maxCount = 5;
     int timeOutSec = 0;