From 19fcec84d8d7d21e796c7624e521b60d28ee21ed Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 20:45:59 +0200
Subject: Adding upstream version 16.2.11+ds.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../persistent_cache/volatile_tier_impl.h          | 142 +++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 src/rocksdb/utilities/persistent_cache/volatile_tier_impl.h

(limited to 'src/rocksdb/utilities/persistent_cache/volatile_tier_impl.h')

diff --git a/src/rocksdb/utilities/persistent_cache/volatile_tier_impl.h b/src/rocksdb/utilities/persistent_cache/volatile_tier_impl.h
new file mode 100644
index 000000000..6116e894b
--- /dev/null
+++ b/src/rocksdb/utilities/persistent_cache/volatile_tier_impl.h
@@ -0,0 +1,142 @@
+//  Copyright (c) 2013, 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).
+//
+#pragma once
+
+#ifndef ROCKSDB_LITE
+
+#include <atomic>
+#include <limits>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "rocksdb/cache.h"
+#include "utilities/persistent_cache/hash_table.h"
+#include "utilities/persistent_cache/hash_table_evictable.h"
+#include "utilities/persistent_cache/persistent_cache_tier.h"
+
+// VolatileCacheTier
+//
+// This file provides persistent cache tier implementation for caching
+// key/values in RAM.
+//
+//        key/values
+//           |
+//           V
+// +-------------------+
+// | VolatileCacheTier | Store in an evictable hash table
+// +-------------------+
+//           |
+//           V
+//       on eviction
+//   pushed to next tier
+//
+// The implementation is designed to be concurrent. The evictable hash table
+// implementation is not concurrent at this point though.
+//
+// The eviction algorithm is LRU
+namespace ROCKSDB_NAMESPACE {
+
+class VolatileCacheTier : public PersistentCacheTier {
+ public:
+  explicit VolatileCacheTier(
+      const bool is_compressed = true,
+      const size_t max_size = std::numeric_limits<size_t>::max())
+      : is_compressed_(is_compressed), max_size_(max_size) {}
+
+  virtual ~VolatileCacheTier();
+
+  // insert to cache
+  Status Insert(const Slice& page_key, const char* data,
+                const size_t size) override;
+  // lookup key in cache
+  Status Lookup(const Slice& page_key, std::unique_ptr<char[]>* data,
+                size_t* size) override;
+
+  // is compressed cache ?
+  bool IsCompressed() override { return is_compressed_; }
+
+  // erase key from cache
+  bool Erase(const Slice& key) override;
+
+  std::string GetPrintableOptions() const override {
+    return "VolatileCacheTier";
+  }
+
+  // Expose stats as map
+  PersistentCache::StatsType Stats() override;
+
+ private:
+  //
+  // Cache data abstraction
+  //
+  struct CacheData : LRUElement<CacheData> {
+    explicit CacheData(CacheData&& rhs) ROCKSDB_NOEXCEPT
+        : key(std::move(rhs.key)),
+          value(std::move(rhs.value)) {}
+
+    explicit CacheData(const std::string& _key, const std::string& _value = "")
+        : key(_key), value(_value) {}
+
+    virtual ~CacheData() {}
+
+    const std::string key;
+    const std::string value;
+  };
+
+  static void DeleteCacheData(CacheData* data);
+
+  //
+  // Index and LRU definition
+  //
+  struct CacheDataHash {
+    uint64_t operator()(const CacheData* obj) const {
+      assert(obj);
+      return std::hash<std::string>()(obj->key);
+    }
+  };
+
+  struct CacheDataEqual {
+    bool operator()(const CacheData* lhs, const CacheData* rhs) const {
+      assert(lhs);
+      assert(rhs);
+      return lhs->key == rhs->key;
+    }
+  };
+
+  struct Statistics {
+    std::atomic<uint64_t> cache_misses_{0};
+    std::atomic<uint64_t> cache_hits_{0};
+    std::atomic<uint64_t> cache_inserts_{0};
+    std::atomic<uint64_t> cache_evicts_{0};
+
+    double CacheHitPct() const {
+      auto lookups = cache_hits_ + cache_misses_;
+      return lookups ? 100 * cache_hits_ / static_cast<double>(lookups) : 0.0;
+    }
+
+    double CacheMissPct() const {
+      auto lookups = cache_hits_ + cache_misses_;
+      return lookups ? 100 * cache_misses_ / static_cast<double>(lookups) : 0.0;
+    }
+  };
+
+  typedef EvictableHashTable<CacheData, CacheDataHash, CacheDataEqual>
+      IndexType;
+
+  // Evict LRU tail
+  bool Evict();
+
+  const bool is_compressed_ = true;    // does it store compressed data
+  IndexType index_;                    // in-memory cache
+  std::atomic<uint64_t> max_size_{0};  // Maximum size of the cache
+  std::atomic<uint64_t> size_{0};      // Size of the cache
+  Statistics stats_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif
-- 
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