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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/rocksdb/utilities/persistent_cache/hash_table_evictable.h | |
parent | Initial commit. (diff) | |
download | ceph-e6918187568dbd01842d8d1d2c808ce16a894239.tar.xz ceph-e6918187568dbd01842d8d1d2c808ce16a894239.zip |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/rocksdb/utilities/persistent_cache/hash_table_evictable.h | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/src/rocksdb/utilities/persistent_cache/hash_table_evictable.h b/src/rocksdb/utilities/persistent_cache/hash_table_evictable.h new file mode 100644 index 000000000..e10939b2f --- /dev/null +++ b/src/rocksdb/utilities/persistent_cache/hash_table_evictable.h @@ -0,0 +1,168 @@ +// 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 <functional> + +#include "util/random.h" +#include "utilities/persistent_cache/hash_table.h" +#include "utilities/persistent_cache/lrulist.h" + +namespace ROCKSDB_NAMESPACE { + +// Evictable Hash Table +// +// Hash table index where least accessed (or one of the least accessed) elements +// can be evicted. +// +// Please note EvictableHashTable can only be created for pointer type objects +template <class T, class Hash, class Equal> +class EvictableHashTable : private HashTable<T*, Hash, Equal> { + public: + using hash_table = HashTable<T*, Hash, Equal>; + + explicit EvictableHashTable(const size_t capacity = 1024 * 1024, + const float load_factor = 2.0, + const uint32_t nlocks = 256) + : HashTable<T*, Hash, Equal>(capacity, load_factor, nlocks), + lru_lists_(new LRUList<T>[hash_table::nlocks_]) { + assert(lru_lists_); + } + + virtual ~EvictableHashTable() { AssertEmptyLRU(); } + + // + // Insert given record to hash table (and LRU list) + // + bool Insert(T* t) { + const uint64_t h = Hash()(t); + typename hash_table::Bucket& bucket = GetBucket(h); + LRUListType& lru = GetLRUList(h); + port::RWMutex& lock = GetMutex(h); + + WriteLock _(&lock); + if (hash_table::Insert(&bucket, t)) { + lru.Push(t); + return true; + } + return false; + } + + // + // Lookup hash table + // + // Please note that read lock should be held by the caller. This is because + // the caller owns the data, and should hold the read lock as long as he + // operates on the data. + bool Find(T* t, T** ret) { + const uint64_t h = Hash()(t); + typename hash_table::Bucket& bucket = GetBucket(h); + LRUListType& lru = GetLRUList(h); + port::RWMutex& lock = GetMutex(h); + + ReadLock _(&lock); + if (hash_table::Find(&bucket, t, ret)) { + ++(*ret)->refs_; + lru.Touch(*ret); + return true; + } + return false; + } + + // + // Evict one of the least recently used object + // + T* Evict(const std::function<void(T*)>& fn = nullptr) { + uint32_t random = Random::GetTLSInstance()->Next(); + const size_t start_idx = random % hash_table::nlocks_; + T* t = nullptr; + + // iterate from start_idx .. 0 .. start_idx + for (size_t i = 0; !t && i < hash_table::nlocks_; ++i) { + const size_t idx = (start_idx + i) % hash_table::nlocks_; + + WriteLock _(&hash_table::locks_[idx]); + LRUListType& lru = lru_lists_[idx]; + if (!lru.IsEmpty() && (t = lru.Pop()) != nullptr) { + assert(!t->refs_); + // We got an item to evict, erase from the bucket + const uint64_t h = Hash()(t); + typename hash_table::Bucket& bucket = GetBucket(h); + T* tmp = nullptr; + bool status = hash_table::Erase(&bucket, t, &tmp); + assert(t == tmp); + (void)status; + assert(status); + if (fn) { + fn(t); + } + break; + } + assert(!t); + } + return t; + } + + void Clear(void (*fn)(T*)) { + for (uint32_t i = 0; i < hash_table::nbuckets_; ++i) { + const uint32_t lock_idx = i % hash_table::nlocks_; + WriteLock _(&hash_table::locks_[lock_idx]); + auto& lru_list = lru_lists_[lock_idx]; + auto& bucket = hash_table::buckets_[i]; + for (auto* t : bucket.list_) { + lru_list.Unlink(t); + (*fn)(t); + } + bucket.list_.clear(); + } + // make sure that all LRU lists are emptied + AssertEmptyLRU(); + } + + void AssertEmptyLRU() { +#ifndef NDEBUG + for (uint32_t i = 0; i < hash_table::nlocks_; ++i) { + WriteLock _(&hash_table::locks_[i]); + auto& lru_list = lru_lists_[i]; + assert(lru_list.IsEmpty()); + } +#endif + } + + // + // Fetch the mutex associated with a key + // This call is used to hold the lock for a given data for extended period of + // time. + port::RWMutex* GetMutex(T* t) { return hash_table::GetMutex(t); } + + private: + using LRUListType = LRUList<T>; + + typename hash_table::Bucket& GetBucket(const uint64_t h) { + const uint32_t bucket_idx = h % hash_table::nbuckets_; + return hash_table::buckets_[bucket_idx]; + } + + LRUListType& GetLRUList(const uint64_t h) { + const uint32_t bucket_idx = h % hash_table::nbuckets_; + const uint32_t lock_idx = bucket_idx % hash_table::nlocks_; + return lru_lists_[lock_idx]; + } + + port::RWMutex& GetMutex(const uint64_t h) { + const uint32_t bucket_idx = h % hash_table::nbuckets_; + const uint32_t lock_idx = bucket_idx % hash_table::nlocks_; + return hash_table::locks_[lock_idx]; + } + + std::unique_ptr<LRUListType[]> lru_lists_; +}; + +} // namespace ROCKSDB_NAMESPACE + +#endif |