Fix side effect of Remove operation.

In the original ARC paper, there was no explanation of how Remove should be
handled when the cache is full. The Remove operation would have a side effect
on subsequent Put operations when the cache is not full, which is still
evicting items even though it's clear that there is no need to evict when
the cache is not full.

Now, code has been added to check if the cache is full to avoid performance
degradation.

- fix c_, it should be max_count.
- add unittest.
- use list::splice to avoid copying value
- add suffix to member fields list and map

Signed-off-by: Xu Yifeng <[email protected]>

curvefs/test/common/arc_cache_test.cpp

@@ -0,0 +1,204 @@
+/*
+ *  Copyright (c) 2020 NetEase Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+/*
+ * Project: curve
+ * Created Date: 20231213
+ * Author: xuyifeng
+ */
+
+#include <gtest/gtest.h>
+#include <glog/logging.h>
+#include <cstdint>
+
+#include "src/common/lru_cache.h"
+
+namespace curve {
+namespace common {
+
+static void
+assert_cache_metrics(std::shared_ptr<ARCCache<int, int>> cache) {
+    auto metrics = cache->GetCacheMetrics();
+    auto arcSize = cache->ArcSize();
+    /* sizeof(key) + sizeof(value), yet sizeof(int) + sizeof(value) */
+    auto sizeofKey = sizeof(int);
+    auto sizeofValue = sizeof(int);
+    ASSERT_EQ(arcSize.BSize() * sizeofKey +
+            arcSize.TSize() * (sizeofKey + sizeofValue),
+            metrics->cacheBytes.get_value());
+}
+
+TEST(ArcTest, test_cache_create) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+
+    ASSERT_EQ(cache->Capacity(), 5);
+    ASSERT_EQ(cache->Size(), 0);
+}
+
+TEST(ArcTest, test_cache_put) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount; ++i) {
+        cache->Put(i, i);
+    }
+
+    ASSERT_TRUE(cache->Size() == maxCount);
+
+    int v;
+    for (int i = 0; i < maxCount; ++i) {
+        ASSERT_TRUE(cache->Get(i, &v));
+        ASSERT_EQ(v, i);
+    }
+
+    // run again trigger Touch() internally
+    for (int i = 0; i < maxCount; ++i) {
+        ASSERT_TRUE(cache->Get(i, &v));
+        ASSERT_EQ(v, i);
+    }
+
+    assert_cache_metrics(cache);
+}
+
+TEST(ArcTest, test_cache_getlast) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount; ++i) {
+        cache->Put(i, i);
+    }
+
+    for (int i = 0; i < maxCount; ++i) {
+        int k;
+        ASSERT_TRUE(cache->GetLast(i, &k));
+        ASSERT_EQ(k, i);
+    }
+}
+
+TEST(ArcTest, test_cache_getlast2) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount; ++i) {
+        cache->Put(i, i);
+    }
+
+    int k, v;
+    ASSERT_TRUE(cache->GetLast(&k, &v));
+    ASSERT_EQ(k, 0);
+    ASSERT_EQ(v, 0);
+}
+
+static bool filter_check_3(const int &v) {
+    return v == 3;
+}
+
+TEST(ArcTest, test_cache_getlast3) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount; ++i) {
+        cache->Put(i, i);
+    }
+
+    int k, v;
+    ASSERT_TRUE(cache->GetLast(&k, &v, filter_check_3));
+    ASSERT_EQ(k, 3);
+    ASSERT_EQ(v, 3);
+}
+
+TEST(ArcTest, test_cache_retire) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount+1; ++i) {
+        cache->Put(i, i);
+    }
+
+    ASSERT_TRUE(cache->Size() == maxCount);
+
+    int v;
+    ASSERT_TRUE(cache->Get(0, &v) == false);
+    for (int i = 1; i < maxCount+1; ++i) {
+        ASSERT_TRUE(cache->Get(i, &v));
+        ASSERT_EQ(v, i);
+    }
+
+    int removed_count = 0;
+    for (int i = 100; i < 200; ++i) {
+        int removed;
+        int ret = cache->Put(i, i, &removed);
+        if (ret) {
+            removed_count++;
+            // This checks Arc cache's scan-resistent behavior,
+            // first an item in t2 is eliminated, after that,
+            // items in t1 is replaced
+            ASSERT_TRUE(removed == 1 || removed >= 100);
+        }
+        (void)removed;
+    }
+    ASSERT_EQ(removed_count, (200 - 100));
+
+    auto s = cache->ArcSize();
+    ASSERT_TRUE(s.BSize() + s.TSize() <= 2 * maxCount);
+
+    assert_cache_metrics(cache);
+}
+
+TEST(ArcTest, test_cache_remove) {
+    int maxCount = 5;
+    auto cache = std::make_shared<ARCCache<int, int>>(maxCount,
+        std::make_shared<CacheMetrics>("Cache"));
+    auto metrics = cache->GetCacheMetrics();
+
+    for (int i = 0; i < maxCount; ++i) {
+        cache->Put(i, i);
+    }
+
+    cache->Remove(0);
+    int v;
+    ASSERT_FALSE(cache->Get(0, &v));
+    ASSERT_TRUE(cache->Size() == maxCount-1);
+
+    for (int i = 1; i < maxCount; ++i) {
+        ASSERT_TRUE(cache->Get(i, &v));
+        ASSERT_EQ(v, i);
+    }
+
+    for (int i = 100; i < 200; ++i) {
+        cache->Put(i, i);
+    }
+
+    auto s = cache->ArcSize();
+    ASSERT_TRUE(s.BSize() + s.TSize() <= 2 * maxCount);
+    assert_cache_metrics(cache);
+}
+
+}  // namespace common
+}  // namespace curve
+