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// 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.
#include "cache/sharded_cache.h"
#include <algorithm>
#include <cstdint>
#include <memory>
#include "util/hash.h"
#include "util/math.h"
#include "util/mutexlock.h"
namespace ROCKSDB_NAMESPACE {
ShardedCacheBase::ShardedCacheBase(size_t capacity, int num_shard_bits,
bool strict_capacity_limit,
std::shared_ptr<MemoryAllocator> allocator)
: Cache(std::move(allocator)),
last_id_(1),
shard_mask_((uint32_t{1} << num_shard_bits) - 1),
strict_capacity_limit_(strict_capacity_limit),
capacity_(capacity) {}
size_t ShardedCacheBase::ComputePerShardCapacity(size_t capacity) const {
uint32_t num_shards = GetNumShards();
return (capacity + (num_shards - 1)) / num_shards;
}
size_t ShardedCacheBase::GetPerShardCapacity() const {
return ComputePerShardCapacity(GetCapacity());
}
uint64_t ShardedCacheBase::NewId() {
return last_id_.fetch_add(1, std::memory_order_relaxed);
}
size_t ShardedCacheBase::GetCapacity() const {
MutexLock l(&config_mutex_);
return capacity_;
}
bool ShardedCacheBase::HasStrictCapacityLimit() const {
MutexLock l(&config_mutex_);
return strict_capacity_limit_;
}
size_t ShardedCacheBase::GetUsage(Handle* handle) const {
return GetCharge(handle);
}
std::string ShardedCacheBase::GetPrintableOptions() const {
std::string ret;
ret.reserve(20000);
const int kBufferSize = 200;
char buffer[kBufferSize];
{
MutexLock l(&config_mutex_);
snprintf(buffer, kBufferSize, " capacity : %" ROCKSDB_PRIszt "\n",
capacity_);
ret.append(buffer);
snprintf(buffer, kBufferSize, " num_shard_bits : %d\n",
GetNumShardBits());
ret.append(buffer);
snprintf(buffer, kBufferSize, " strict_capacity_limit : %d\n",
strict_capacity_limit_);
ret.append(buffer);
}
snprintf(buffer, kBufferSize, " memory_allocator : %s\n",
memory_allocator() ? memory_allocator()->Name() : "None");
ret.append(buffer);
AppendPrintableOptions(ret);
return ret;
}
int GetDefaultCacheShardBits(size_t capacity, size_t min_shard_size) {
int num_shard_bits = 0;
size_t num_shards = capacity / min_shard_size;
while (num_shards >>= 1) {
if (++num_shard_bits >= 6) {
// No more than 6.
return num_shard_bits;
}
}
return num_shard_bits;
}
int ShardedCacheBase::GetNumShardBits() const {
return BitsSetToOne(shard_mask_);
}
uint32_t ShardedCacheBase::GetNumShards() const { return shard_mask_ + 1; }
} // namespace ROCKSDB_NAMESPACE
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