Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 546 insertions, 0 deletions

diff --git a/src/rocksdb/cache/lru_cache.h b/src/rocksdb/cache/lru_cache.h
new file mode 100644
index 000000000..99b2f2b20
--- /dev/null
+++ b/src/rocksdb/cache/lru_cache.h
@@ -0,0 +1,546 @@
+//  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).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include <memory>
+#include <string>
+
+#include "cache/sharded_cache.h"
+#include "port/lang.h"
+#include "port/malloc.h"
+#include "port/port.h"
+#include "rocksdb/secondary_cache.h"
+#include "util/autovector.h"
+#include "util/distributed_mutex.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace lru_cache {
+
+// LRU cache implementation. This class is not thread-safe.
+
+// An entry is a variable length heap-allocated structure.
+// Entries are referenced by cache and/or by any external entity.
+// The cache keeps all its entries in a hash table. Some elements
+// are also stored on LRU list.
+//
+// LRUHandle can be in these states:
+// 1. Referenced externally AND in hash table.
+//    In that case the entry is *not* in the LRU list
+//    (refs >= 1 && in_cache == true)
+// 2. Not referenced externally AND in hash table.
+//    In that case the entry is in the LRU list and can be freed.
+//    (refs == 0 && in_cache == true)
+// 3. Referenced externally AND not in hash table.
+//    In that case the entry is not in the LRU list and not in hash table.
+//    The entry must be freed if refs becomes 0 in this state.
+//    (refs >= 1 && in_cache == false)
+// If you call LRUCacheShard::Release enough times on an entry in state 1, it
+// will go into state 2. To move from state 1 to state 3, either call
+// LRUCacheShard::Erase or LRUCacheShard::Insert with the same key (but
+// possibly different value). To move from state 2 to state 1, use
+// LRUCacheShard::Lookup.
+// While refs > 0, public properties like value and deleter must not change.
+
+struct LRUHandle {
+  void* value;
+  union Info {
+    Info() {}
+    ~Info() {}
+    Cache::DeleterFn deleter;
+    const Cache::CacheItemHelper* helper;
+  } info_;
+  // An entry is not added to the LRUHandleTable until the secondary cache
+  // lookup is complete, so its safe to have this union.
+  union {
+    LRUHandle* next_hash;
+    SecondaryCacheResultHandle* sec_handle;
+  };
+  LRUHandle* next;
+  LRUHandle* prev;
+  size_t total_charge;  // TODO(opt): Only allow uint32_t?
+  size_t key_length;
+  // The hash of key(). Used for fast sharding and comparisons.
+  uint32_t hash;
+  // The number of external refs to this entry. The cache itself is not counted.
+  uint32_t refs;
+
+  // Mutable flags - access controlled by mutex
+  // The m_ and M_ prefixes (and im_ and IM_ later) are to hopefully avoid
+  // checking an M_ flag on im_flags or an IM_ flag on m_flags.
+  uint8_t m_flags;
+  enum MFlags : uint8_t {
+    // Whether this entry is referenced by the hash table.
+    M_IN_CACHE = (1 << 0),
+    // Whether this entry has had any lookups (hits).
+    M_HAS_HIT = (1 << 1),
+    // Whether this entry is in high-pri pool.
+    M_IN_HIGH_PRI_POOL = (1 << 2),
+    // Whether this entry is in low-pri pool.
+    M_IN_LOW_PRI_POOL = (1 << 3),
+  };
+
+  // "Immutable" flags - only set in single-threaded context and then
+  // can be accessed without mutex
+  uint8_t im_flags;
+  enum ImFlags : uint8_t {
+    // Whether this entry is high priority entry.
+    IM_IS_HIGH_PRI = (1 << 0),
+    // Whether this entry is low priority entry.
+    IM_IS_LOW_PRI = (1 << 1),
+    // Can this be inserted into the secondary cache.
+    IM_IS_SECONDARY_CACHE_COMPATIBLE = (1 << 2),
+    // Is the handle still being read from a lower tier.
+    IM_IS_PENDING = (1 << 3),
+    // Whether this handle is still in a lower tier
+    IM_IS_IN_SECONDARY_CACHE = (1 << 4),
+    // Marks result handles that should not be inserted into cache
+    IM_IS_STANDALONE = (1 << 5),
+  };
+
+  // Beginning of the key (MUST BE THE LAST FIELD IN THIS STRUCT!)
+  char key_data[1];
+
+  Slice key() const { return Slice(key_data, key_length); }
+
+  // For HandleImpl concept
+  uint32_t GetHash() const { return hash; }
+
+  // Increase the reference count by 1.
+  void Ref() { refs++; }
+
+  // Just reduce the reference count by 1. Return true if it was last reference.
+  bool Unref() {
+    assert(refs > 0);
+    refs--;
+    return refs == 0;
+  }
+
+  // Return true if there are external refs, false otherwise.
+  bool HasRefs() const { return refs > 0; }
+
+  bool InCache() const { return m_flags & M_IN_CACHE; }
+  bool IsHighPri() const { return im_flags & IM_IS_HIGH_PRI; }
+  bool InHighPriPool() const { return m_flags & M_IN_HIGH_PRI_POOL; }
+  bool IsLowPri() const { return im_flags & IM_IS_LOW_PRI; }
+  bool InLowPriPool() const { return m_flags & M_IN_LOW_PRI_POOL; }
+  bool HasHit() const { return m_flags & M_HAS_HIT; }
+  bool IsSecondaryCacheCompatible() const {
+    return im_flags & IM_IS_SECONDARY_CACHE_COMPATIBLE;
+  }
+  bool IsPending() const { return im_flags & IM_IS_PENDING; }
+  bool IsInSecondaryCache() const {
+    return im_flags & IM_IS_IN_SECONDARY_CACHE;
+  }
+  bool IsStandalone() const { return im_flags & IM_IS_STANDALONE; }
+
+  void SetInCache(bool in_cache) {
+    if (in_cache) {
+      m_flags |= M_IN_CACHE;
+    } else {
+      m_flags &= ~M_IN_CACHE;
+    }
+  }
+
+  void SetPriority(Cache::Priority priority) {
+    if (priority == Cache::Priority::HIGH) {
+      im_flags |= IM_IS_HIGH_PRI;
+      im_flags &= ~IM_IS_LOW_PRI;
+    } else if (priority == Cache::Priority::LOW) {
+      im_flags &= ~IM_IS_HIGH_PRI;
+      im_flags |= IM_IS_LOW_PRI;
+    } else {
+      im_flags &= ~IM_IS_HIGH_PRI;
+      im_flags &= ~IM_IS_LOW_PRI;
+    }
+  }
+
+  void SetInHighPriPool(bool in_high_pri_pool) {
+    if (in_high_pri_pool) {
+      m_flags |= M_IN_HIGH_PRI_POOL;
+    } else {
+      m_flags &= ~M_IN_HIGH_PRI_POOL;
+    }
+  }
+
+  void SetInLowPriPool(bool in_low_pri_pool) {
+    if (in_low_pri_pool) {
+      m_flags |= M_IN_LOW_PRI_POOL;
+    } else {
+      m_flags &= ~M_IN_LOW_PRI_POOL;
+    }
+  }
+
+  void SetHit() { m_flags |= M_HAS_HIT; }
+
+  void SetSecondaryCacheCompatible(bool compat) {
+    if (compat) {
+      im_flags |= IM_IS_SECONDARY_CACHE_COMPATIBLE;
+    } else {
+      im_flags &= ~IM_IS_SECONDARY_CACHE_COMPATIBLE;
+    }
+  }
+
+  void SetIsPending(bool pending) {
+    if (pending) {
+      im_flags |= IM_IS_PENDING;
+    } else {
+      im_flags &= ~IM_IS_PENDING;
+    }
+  }
+
+  void SetIsInSecondaryCache(bool is_in_secondary_cache) {
+    if (is_in_secondary_cache) {
+      im_flags |= IM_IS_IN_SECONDARY_CACHE;
+    } else {
+      im_flags &= ~IM_IS_IN_SECONDARY_CACHE;
+    }
+  }
+
+  void SetIsStandalone(bool is_standalone) {
+    if (is_standalone) {
+      im_flags |= IM_IS_STANDALONE;
+    } else {
+      im_flags &= ~IM_IS_STANDALONE;
+    }
+  }
+
+  void Free() {
+    assert(refs == 0);
+
+    if (!IsSecondaryCacheCompatible() && info_.deleter) {
+      (*info_.deleter)(key(), value);
+    } else if (IsSecondaryCacheCompatible()) {
+      if (IsPending()) {
+        assert(sec_handle != nullptr);
+        SecondaryCacheResultHandle* tmp_sec_handle = sec_handle;
+        tmp_sec_handle->Wait();
+        value = tmp_sec_handle->Value();
+        delete tmp_sec_handle;
+      }
+      if (value) {
+        (*info_.helper->del_cb)(key(), value);
+      }
+    }
+
+    free(this);
+  }
+
+  inline size_t CalcuMetaCharge(
+      CacheMetadataChargePolicy metadata_charge_policy) const {
+    if (metadata_charge_policy != kFullChargeCacheMetadata) {
+      return 0;
+    } else {
+#ifdef ROCKSDB_MALLOC_USABLE_SIZE
+      return malloc_usable_size(
+          const_cast<void*>(static_cast<const void*>(this)));
+#else
+      // This is the size that is used when a new handle is created.
+      return sizeof(LRUHandle) - 1 + key_length;
+#endif
+    }
+  }
+
+  // Calculate the memory usage by metadata.
+  inline void CalcTotalCharge(
+      size_t charge, CacheMetadataChargePolicy metadata_charge_policy) {
+    total_charge = charge + CalcuMetaCharge(metadata_charge_policy);
+  }
+
+  inline size_t GetCharge(
+      CacheMetadataChargePolicy metadata_charge_policy) const {
+    size_t meta_charge = CalcuMetaCharge(metadata_charge_policy);
+    assert(total_charge >= meta_charge);
+    return total_charge - meta_charge;
+  }
+};
+
+// We provide our own simple hash table since it removes a whole bunch
+// of porting hacks and is also faster than some of the built-in hash
+// table implementations in some of the compiler/runtime combinations
+// we have tested.  E.g., readrandom speeds up by ~5% over the g++
+// 4.4.3's builtin hashtable.
+class LRUHandleTable {
+ public:
+  explicit LRUHandleTable(int max_upper_hash_bits);
+  ~LRUHandleTable();
+
+  LRUHandle* Lookup(const Slice& key, uint32_t hash);
+  LRUHandle* Insert(LRUHandle* h);
+  LRUHandle* Remove(const Slice& key, uint32_t hash);
+
+  template <typename T>
+  void ApplyToEntriesRange(T func, size_t index_begin, size_t index_end) {
+    for (size_t i = index_begin; i < index_end; i++) {
+      LRUHandle* h = list_[i];
+      while (h != nullptr) {
+        auto n = h->next_hash;
+        assert(h->InCache());
+        func(h);
+        h = n;
+      }
+    }
+  }
+
+  int GetLengthBits() const { return length_bits_; }
+
+  size_t GetOccupancyCount() const { return elems_; }
+
+ private:
+  // Return a pointer to slot that points to a cache entry that
+  // matches key/hash.  If there is no such cache entry, return a
+  // pointer to the trailing slot in the corresponding linked list.
+  LRUHandle** FindPointer(const Slice& key, uint32_t hash);
+
+  void Resize();
+
+  // Number of hash bits (upper because lower bits used for sharding)
+  // used for table index. Length == 1 << length_bits_
+  int length_bits_;
+
+  // The table consists of an array of buckets where each bucket is
+  // a linked list of cache entries that hash into the bucket.
+  std::unique_ptr<LRUHandle*[]> list_;
+
+  // Number of elements currently in the table.
+  uint32_t elems_;
+
+  // Set from max_upper_hash_bits (see constructor).
+  const int max_length_bits_;
+};
+
+// A single shard of sharded cache.
+class ALIGN_AS(CACHE_LINE_SIZE) LRUCacheShard final : public CacheShardBase {
+ public:
+  LRUCacheShard(size_t capacity, bool strict_capacity_limit,
+                double high_pri_pool_ratio, double low_pri_pool_ratio,
+                bool use_adaptive_mutex,
+                CacheMetadataChargePolicy metadata_charge_policy,
+                int max_upper_hash_bits, SecondaryCache* secondary_cache);
+
+ public:  // Type definitions expected as parameter to ShardedCache
+  using HandleImpl = LRUHandle;
+  using HashVal = uint32_t;
+  using HashCref = uint32_t;
+
+ public:  // Function definitions expected as parameter to ShardedCache
+  static inline HashVal ComputeHash(const Slice& key) {
+    return Lower32of64(GetSliceNPHash64(key));
+  }
+
+  // Separate from constructor so caller can easily make an array of LRUCache
+  // if current usage is more than new capacity, the function will attempt to
+  // free the needed space.
+  void SetCapacity(size_t capacity);
+
+  // Set the flag to reject insertion if cache if full.
+  void SetStrictCapacityLimit(bool strict_capacity_limit);
+
+  // Set percentage of capacity reserved for high-pri cache entries.
+  void SetHighPriorityPoolRatio(double high_pri_pool_ratio);
+
+  // Set percentage of capacity reserved for low-pri cache entries.
+  void SetLowPriorityPoolRatio(double low_pri_pool_ratio);
+
+  // Like Cache methods, but with an extra "hash" parameter.
+  inline Status Insert(const Slice& key, uint32_t hash, void* value,
+                       size_t charge, Cache::DeleterFn deleter,
+                       LRUHandle** handle, Cache::Priority priority) {
+    return Insert(key, hash, value, charge, deleter, nullptr, handle, priority);
+  }
+  inline Status Insert(const Slice& key, uint32_t hash, void* value,
+                       const Cache::CacheItemHelper* helper, size_t charge,
+                       LRUHandle** handle, Cache::Priority priority) {
+    assert(helper);
+    return Insert(key, hash, value, charge, nullptr, helper, handle, priority);
+  }
+  // If helper_cb is null, the values of the following arguments don't matter.
+  LRUHandle* Lookup(const Slice& key, uint32_t hash,
+                    const Cache::CacheItemHelper* helper,
+                    const Cache::CreateCallback& create_cb,
+                    Cache::Priority priority, bool wait, Statistics* stats);
+  inline LRUHandle* Lookup(const Slice& key, uint32_t hash) {
+    return Lookup(key, hash, nullptr, nullptr, Cache::Priority::LOW, true,
+                  nullptr);
+  }
+  bool Release(LRUHandle* handle, bool useful, bool erase_if_last_ref);
+  bool IsReady(LRUHandle* /*handle*/);
+  void Wait(LRUHandle* /*handle*/) {}
+  bool Ref(LRUHandle* handle);
+  void Erase(const Slice& key, uint32_t hash);
+
+  // Although in some platforms the update of size_t is atomic, to make sure
+  // GetUsage() and GetPinnedUsage() work correctly under any platform, we'll
+  // protect them with mutex_.
+
+  size_t GetUsage() const;
+  size_t GetPinnedUsage() const;
+  size_t GetOccupancyCount() const;
+  size_t GetTableAddressCount() const;
+
+  void ApplyToSomeEntries(
+      const std::function<void(const Slice& key, void* value, size_t charge,
+                               DeleterFn deleter)>& callback,
+      size_t average_entries_per_lock, size_t* state);
+
+  void EraseUnRefEntries();
+
+ public:  // other function definitions
+  void TEST_GetLRUList(LRUHandle** lru, LRUHandle** lru_low_pri,
+                       LRUHandle** lru_bottom_pri);
+
+  // Retrieves number of elements in LRU, for unit test purpose only.
+  // Not threadsafe.
+  size_t TEST_GetLRUSize();
+
+  // Retrieves high pri pool ratio
+  double GetHighPriPoolRatio();
+
+  // Retrieves low pri pool ratio
+  double GetLowPriPoolRatio();
+
+  void AppendPrintableOptions(std::string& /*str*/) const;
+
+ private:
+  friend class LRUCache;
+  // Insert an item into the hash table and, if handle is null, insert into
+  // the LRU list. Older items are evicted as necessary. If the cache is full
+  // and free_handle_on_fail is true, the item is deleted and handle is set to
+  // nullptr.
+  Status InsertItem(LRUHandle* item, LRUHandle** handle,
+                    bool free_handle_on_fail);
+  Status Insert(const Slice& key, uint32_t hash, void* value, size_t charge,
+                DeleterFn deleter, const Cache::CacheItemHelper* helper,
+                LRUHandle** handle, Cache::Priority priority);
+  // Promote an item looked up from the secondary cache to the LRU cache.
+  // The item may be still in the secondary cache.
+  // It is only inserted into the hash table and not the LRU list, and only
+  // if the cache is not at full capacity, as is the case during Insert.  The
+  // caller should hold a reference on the LRUHandle. When the caller releases
+  // the last reference, the item is added to the LRU list.
+  // The item is promoted to the high pri or low pri pool as specified by the
+  // caller in Lookup.
+  void Promote(LRUHandle* e);
+  void LRU_Remove(LRUHandle* e);
+  void LRU_Insert(LRUHandle* e);
+
+  // Overflow the last entry in high-pri pool to low-pri pool until size of
+  // high-pri pool is no larger than the size specify by high_pri_pool_pct.
+  void MaintainPoolSize();
+
+  // Free some space following strict LRU policy until enough space
+  // to hold (usage_ + charge) is freed or the lru list is empty
+  // This function is not thread safe - it needs to be executed while
+  // holding the mutex_.
+  void EvictFromLRU(size_t charge, autovector<LRUHandle*>* deleted);
+
+  // Try to insert the evicted handles into the secondary cache.
+  void TryInsertIntoSecondaryCache(autovector<LRUHandle*> evicted_handles);
+
+  // Initialized before use.
+  size_t capacity_;
+
+  // Memory size for entries in high-pri pool.
+  size_t high_pri_pool_usage_;
+
+  // Memory size for entries in low-pri pool.
+  size_t low_pri_pool_usage_;
+
+  // Whether to reject insertion if cache reaches its full capacity.
+  bool strict_capacity_limit_;
+
+  // Ratio of capacity reserved for high priority cache entries.
+  double high_pri_pool_ratio_;
+
+  // High-pri pool size, equals to capacity * high_pri_pool_ratio.
+  // Remember the value to avoid recomputing each time.
+  double high_pri_pool_capacity_;
+
+  // Ratio of capacity reserved for low priority cache entries.
+  double low_pri_pool_ratio_;
+
+  // Low-pri pool size, equals to capacity * low_pri_pool_ratio.
+  // Remember the value to avoid recomputing each time.
+  double low_pri_pool_capacity_;
+
+  // Dummy head of LRU list.
+  // lru.prev is newest entry, lru.next is oldest entry.
+  // LRU contains items which can be evicted, ie reference only by cache
+  LRUHandle lru_;
+
+  // Pointer to head of low-pri pool in LRU list.
+  LRUHandle* lru_low_pri_;
+
+  // Pointer to head of bottom-pri pool in LRU list.
+  LRUHandle* lru_bottom_pri_;
+
+  // ------------^^^^^^^^^^^^^-----------
+  // Not frequently modified data members
+  // ------------------------------------
+  //
+  // We separate data members that are updated frequently from the ones that
+  // are not frequently updated so that they don't share the same cache line
+  // which will lead into false cache sharing
+  //
+  // ------------------------------------
+  // Frequently modified data members
+  // ------------vvvvvvvvvvvvv-----------
+  LRUHandleTable table_;
+
+  // Memory size for entries residing in the cache.
+  size_t usage_;
+
+  // Memory size for entries residing only in the LRU list.
+  size_t lru_usage_;
+
+  // mutex_ protects the following state.
+  // We don't count mutex_ as the cache's internal state so semantically we
+  // don't mind mutex_ invoking the non-const actions.
+  mutable DMutex mutex_;
+
+  // Owned by LRUCache
+  SecondaryCache* secondary_cache_;
+};
+
+class LRUCache
+#ifdef NDEBUG
+    final
+#endif
+    : public ShardedCache<LRUCacheShard> {
+ public:
+  LRUCache(size_t capacity, int num_shard_bits, bool strict_capacity_limit,
+           double high_pri_pool_ratio, double low_pri_pool_ratio,
+           std::shared_ptr<MemoryAllocator> memory_allocator = nullptr,
+           bool use_adaptive_mutex = kDefaultToAdaptiveMutex,
+           CacheMetadataChargePolicy metadata_charge_policy =
+               kDontChargeCacheMetadata,
+           std::shared_ptr<SecondaryCache> secondary_cache = nullptr);
+  const char* Name() const override { return "LRUCache"; }
+  void* Value(Handle* handle) override;
+  size_t GetCharge(Handle* handle) const override;
+  DeleterFn GetDeleter(Handle* handle) const override;
+  void WaitAll(std::vector<Handle*>& handles) override;
+
+  // Retrieves number of elements in LRU, for unit test purpose only.
+  size_t TEST_GetLRUSize();
+  // Retrieves high pri pool ratio.
+  double GetHighPriPoolRatio();
+
+  void AppendPrintableOptions(std::string& str) const override;
+
+ private:
+  std::shared_ptr<SecondaryCache> secondary_cache_;
+};
+
+}  // namespace lru_cache
+
+using LRUCache = lru_cache::LRUCache;
+using LRUHandle = lru_cache::LRUHandle;
+using LRUCacheShard = lru_cache::LRUCacheShard;
+
+}  // namespace ROCKSDB_NAMESPACE