mirror of https://github.com/facebook/rocksdb.git
71 lines
2.3 KiB
C++
71 lines
2.3 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "dynamic_bloom.h"
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#include <algorithm>
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#include "memory/allocator.h"
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#include "port/port.h"
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#include "rocksdb/slice.h"
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#include "util/hash.h"
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namespace ROCKSDB_NAMESPACE {
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namespace {
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uint32_t roundUpToPow2(uint32_t x) {
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uint32_t rv = 1;
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while (rv < x) {
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rv <<= 1;
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}
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return rv;
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}
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}
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DynamicBloom::DynamicBloom(Allocator* allocator, uint32_t total_bits,
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uint32_t num_probes, size_t huge_page_tlb_size,
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Logger* logger)
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// Round down, except round up with 1
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: kNumDoubleProbes((num_probes + (num_probes == 1)) / 2) {
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assert(num_probes % 2 == 0); // limitation of current implementation
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assert(num_probes <= 10); // limitation of current implementation
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assert(kNumDoubleProbes > 0);
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// Determine how much to round off + align by so that x ^ i (that's xor) is
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// a valid u64 index if x is a valid u64 index and 0 <= i < kNumDoubleProbes.
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uint32_t block_bytes = /*bytes/u64*/ 8 *
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/*u64s*/ std::max(1U, roundUpToPow2(kNumDoubleProbes));
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uint32_t block_bits = block_bytes * 8;
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uint32_t blocks = (total_bits + block_bits - 1) / block_bits;
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uint32_t sz = blocks * block_bytes;
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kLen = sz / /*bytes/u64*/ 8;
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assert(kLen > 0);
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#ifndef NDEBUG
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for (uint32_t i = 0; i < kNumDoubleProbes; ++i) {
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// Ensure probes starting at last word are in range
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assert(((kLen - 1) ^ i) < kLen);
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}
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#endif
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// Padding to correct for allocation not originally aligned on block_bytes
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// boundary
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sz += block_bytes - 1;
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assert(allocator);
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char* raw = allocator->AllocateAligned(sz, huge_page_tlb_size, logger);
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memset(raw, 0, sz);
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auto block_offset = reinterpret_cast<uintptr_t>(raw) % block_bytes;
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if (block_offset > 0) {
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// Align on block_bytes boundary
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raw += block_bytes - block_offset;
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}
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static_assert(sizeof(std::atomic<uint64_t>) == sizeof(uint64_t),
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"Expecting zero-space-overhead atomic");
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data_ = reinterpret_cast<std::atomic<uint64_t>*>(raw);
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}
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} // namespace ROCKSDB_NAMESPACE
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