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rocksdb/util/concurrent_arena.cc

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1.6 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same 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 "util/concurrent_arena.h"
#include <thread>
#include "port/likely.h"
#include "port/port.h"
#include "util/random.h"
namespace rocksdb {
#if ROCKSDB_SUPPORT_THREAD_LOCAL
__thread uint32_t ConcurrentArena::tls_cpuid = 0;
#endif
ConcurrentArena::ConcurrentArena(size_t block_size, size_t huge_page_size)
: shard_block_size_(block_size / 8), arena_(block_size, huge_page_size) {
// find a power of two >= num_cpus and >= 8
auto num_cpus = std::thread::hardware_concurrency();
index_mask_ = 7;
while (index_mask_ + 1 < num_cpus) {
index_mask_ = index_mask_ * 2 + 1;
}
shards_.reset(new Shard[index_mask_ + 1]);
Fixup();
}
ConcurrentArena::Shard* ConcurrentArena::Repick() {
int cpuid = port::PhysicalCoreID();
if (UNLIKELY(cpuid < 0)) {
// cpu id unavailable, just pick randomly
cpuid =
Random::GetTLSInstance()->Uniform(static_cast<int>(index_mask_) + 1);
}
#if ROCKSDB_SUPPORT_THREAD_LOCAL
// even if we are cpu 0, use a non-zero tls_cpuid so we can tell we
// have repicked
tls_cpuid = cpuid | (static_cast<int>(index_mask_) + 1);
#endif
return &shards_[cpuid & index_mask_];
}
} // namespace rocksdb