462796697c
Summary: This patch changes meaning of options.bloom_locality: 0 means disable cache line optimization and any positive number means use CACHE_LINE_SIZE as block size (the previous behavior is the block size will be CACHE_LINE_SIZE*options.bloom_locality). By doing it, the divide operations inside a block can be replaced by a shift. Performance is improved: https://reviews.facebook.net/P471 Also, improve the basic algorithm in two ways: (1) make sure num of blocks is an odd number (2) rotate bytes after every probe in locality mode. Since the divider is 2^n, unless doing it, we are never able to use all the bits. Improvements of false positive: https://reviews.facebook.net/P459 Test Plan: make all check Reviewers: ljin, haobo Reviewed By: haobo Subscribers: dhruba, yhchiang, igor, leveldb Differential Revision: https://reviews.facebook.net/D18843
61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#include "dynamic_bloom.h"
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#include <algorithm>
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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 {
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namespace {
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static uint32_t BloomHash(const Slice& key) {
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return Hash(key.data(), key.size(), 0xbc9f1d34);
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}
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uint32_t GetNumBlocks(uint32_t total_bits) {
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uint32_t num_blocks = (total_bits + CACHE_LINE_SIZE * 8 - 1) /
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(CACHE_LINE_SIZE * 8) * (CACHE_LINE_SIZE * 8);
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// Make num_blocks an odd number to make sure more bits are involved
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// when determining which block.
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if (num_blocks % 2 == 0) {
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num_blocks++;
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}
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return num_blocks;
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}
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}
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DynamicBloom::DynamicBloom(uint32_t total_bits, uint32_t locality,
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uint32_t num_probes,
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uint32_t (*hash_func)(const Slice& key),
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size_t huge_page_tlb_size, Logger* logger)
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: kTotalBits(((locality > 0) ? GetNumBlocks(total_bits) : total_bits + 7) /
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8 * 8),
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kNumBlocks((locality > 0) ? kTotalBits / (CACHE_LINE_SIZE * 8) : 0),
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kNumProbes(num_probes),
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hash_func_(hash_func == nullptr ? &BloomHash : hash_func) {
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assert(kNumBlocks > 0 || kTotalBits > 0);
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assert(kNumProbes > 0);
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uint32_t sz = kTotalBits / 8;
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if (kNumBlocks > 0) {
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sz += CACHE_LINE_SIZE - 1;
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}
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raw_ = reinterpret_cast<unsigned char*>(
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arena_.AllocateAligned(sz, huge_page_tlb_size, logger));
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memset(raw_, 0, sz);
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if (kNumBlocks > 0 && (reinterpret_cast<uint64_t>(raw_) % CACHE_LINE_SIZE)) {
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data_ = raw_ + CACHE_LINE_SIZE -
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reinterpret_cast<uint64_t>(raw_) % CACHE_LINE_SIZE;
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} else {
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data_ = raw_;
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}
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}
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} // rocksdb
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