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diff --git a/src/rocksdb/util/dynamic_bloom.h b/src/rocksdb/util/dynamic_bloom.h
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+++ b/src/rocksdb/util/dynamic_bloom.h
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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).
+
+#pragma once
+
+#include <array>
+#include <string>
+#include "port/port.h"
+#include "rocksdb/slice.h"
+#include "table/multiget_context.h"
+#include "util/hash.h"
+
+#include <atomic>
+#include <memory>
+
+namespace ROCKSDB_NAMESPACE {
+
+class Slice;
+class Allocator;
+class Logger;
+
+// A Bloom filter intended only to be used in memory, never serialized in a way
+// that could lead to schema incompatibility. Supports opt-in lock-free
+// concurrent access.
+//
+// This implementation is also intended for applications generally preferring
+// speed vs. maximum accuracy: roughly 0.9x BF op latency for 1.1x FP rate.
+// For 1% FP rate, that means that the latency of a look-up triggered by an FP
+// should be less than roughly 100x the cost of a Bloom filter op.
+//
+// For simplicity and performance, the current implementation requires
+// num_probes to be a multiple of two and <= 10.
+//
+class DynamicBloom {
+ public:
+  // allocator: pass allocator to bloom filter, hence trace the usage of memory
+  // total_bits: fixed total bits for the bloom
+  // num_probes: number of hash probes for a single key
+  // hash_func:  customized hash function
+  // huge_page_tlb_size:  if >0, try to allocate bloom bytes from huge page TLB
+  //                      within this page size. Need to reserve huge pages for
+  //                      it to be allocated, like:
+  //                         sysctl -w vm.nr_hugepages=20
+  //                     See linux doc Documentation/vm/hugetlbpage.txt
+  explicit DynamicBloom(Allocator* allocator, uint32_t total_bits,
+                        uint32_t num_probes = 6, size_t huge_page_tlb_size = 0,
+                        Logger* logger = nullptr);
+
+  ~DynamicBloom() {}
+
+  // Assuming single threaded access to this function.
+  void Add(const Slice& key);
+
+  // Like Add, but may be called concurrent with other functions.
+  void AddConcurrently(const Slice& key);
+
+  // Assuming single threaded access to this function.
+  void AddHash(uint32_t hash);
+
+  // Like AddHash, but may be called concurrent with other functions.
+  void AddHashConcurrently(uint32_t hash);
+
+  // Multithreaded access to this function is OK
+  bool MayContain(const Slice& key) const;
+
+  void MayContain(int num_keys, Slice** keys, bool* may_match) const;
+
+  // Multithreaded access to this function is OK
+  bool MayContainHash(uint32_t hash) const;
+
+  void Prefetch(uint32_t h);
+
+ private:
+  // Length of the structure, in 64-bit words. For this structure, "word"
+  // will always refer to 64-bit words.
+  uint32_t kLen;
+  // We make the k probes in pairs, two for each 64-bit read/write. Thus,
+  // this stores k/2, the number of words to double-probe.
+  const uint32_t kNumDoubleProbes;
+
+  std::atomic<uint64_t>* data_;
+
+  // or_func(ptr, mask) should effect *ptr |= mask with the appropriate
+  // concurrency safety, working with bytes.
+  template <typename OrFunc>
+  void AddHash(uint32_t hash, const OrFunc& or_func);
+
+  bool DoubleProbe(uint32_t h32, size_t a) const;
+};
+
+inline void DynamicBloom::Add(const Slice& key) { AddHash(BloomHash(key)); }
+
+inline void DynamicBloom::AddConcurrently(const Slice& key) {
+  AddHashConcurrently(BloomHash(key));
+}
+
+inline void DynamicBloom::AddHash(uint32_t hash) {
+  AddHash(hash, [](std::atomic<uint64_t>* ptr, uint64_t mask) {
+    ptr->store(ptr->load(std::memory_order_relaxed) | mask,
+               std::memory_order_relaxed);
+  });
+}
+
+inline void DynamicBloom::AddHashConcurrently(uint32_t hash) {
+  AddHash(hash, [](std::atomic<uint64_t>* ptr, uint64_t mask) {
+    // Happens-before between AddHash and MaybeContains is handled by
+    // access to versions_->LastSequence(), so all we have to do here is
+    // avoid races (so we don't give the compiler a license to mess up
+    // our code) and not lose bits.  std::memory_order_relaxed is enough
+    // for that.
+    if ((mask & ptr->load(std::memory_order_relaxed)) != mask) {
+      ptr->fetch_or(mask, std::memory_order_relaxed);
+    }
+  });
+}
+
+inline bool DynamicBloom::MayContain(const Slice& key) const {
+  return (MayContainHash(BloomHash(key)));
+}
+
+inline void DynamicBloom::MayContain(int num_keys, Slice** keys,
+                                     bool* may_match) const {
+  std::array<uint32_t, MultiGetContext::MAX_BATCH_SIZE> hashes;
+  std::array<size_t, MultiGetContext::MAX_BATCH_SIZE> byte_offsets;
+  for (int i = 0; i < num_keys; ++i) {
+    hashes[i] = BloomHash(*keys[i]);
+    size_t a = fastrange32(kLen, hashes[i]);
+    PREFETCH(data_ + a, 0, 3);
+    byte_offsets[i] = a;
+  }
+
+  for (int i = 0; i < num_keys; i++) {
+    may_match[i] = DoubleProbe(hashes[i], byte_offsets[i]);
+  }
+}
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+// local variable is initialized but not referenced
+#pragma warning(disable : 4189)
+#endif
+inline void DynamicBloom::Prefetch(uint32_t h32) {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+}
+#if defined(_MSC_VER)
+#pragma warning(pop)
+#endif
+
+// Speed hacks in this implementation:
+// * Uses fastrange instead of %
+// * Minimum logic to determine first (and all) probed memory addresses.
+//   (Uses constant bit-xor offsets from the starting probe address.)
+// * (Major) Two probes per 64-bit memory fetch/write.
+//   Code simplification / optimization: only allow even number of probes.
+// * Very fast and effective (murmur-like) hash expansion/re-mixing. (At
+// least on recent CPUs, integer multiplication is very cheap. Each 64-bit
+// remix provides five pairs of bit addresses within a uint64_t.)
+//   Code simplification / optimization: only allow up to 10 probes, from a
+//   single 64-bit remix.
+//
+// The FP rate penalty for this implementation, vs. standard Bloom filter, is
+// roughly 1.12x on top of the 1.15x penalty for a 512-bit cache-local Bloom.
+// This implementation does not explicitly use the cache line size, but is
+// effectively cache-local (up to 16 probes) because of the bit-xor offsetting.
+//
+// NB: could easily be upgraded to support a 64-bit hash and
+// total_bits > 2^32 (512MB). (The latter is a bad idea without the former,
+// because of false positives.)
+
+inline bool DynamicBloom::MayContainHash(uint32_t h32) const {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+  return DoubleProbe(h32, a);
+}
+
+inline bool DynamicBloom::DoubleProbe(uint32_t h32, size_t byte_offset) const {
+  // Expand/remix with 64-bit golden ratio
+  uint64_t h = 0x9e3779b97f4a7c13ULL * h32;
+  for (unsigned i = 0;; ++i) {
+    // Two bit probes per uint64_t probe
+    uint64_t mask =
+        ((uint64_t)1 << (h & 63)) | ((uint64_t)1 << ((h >> 6) & 63));
+    uint64_t val = data_[byte_offset ^ i].load(std::memory_order_relaxed);
+    if (i + 1 >= kNumDoubleProbes) {
+      return (val & mask) == mask;
+    } else if ((val & mask) != mask) {
+      return false;
+    }
+    h = (h >> 12) | (h << 52);
+  }
+}
+
+template <typename OrFunc>
+inline void DynamicBloom::AddHash(uint32_t h32, const OrFunc& or_func) {
+  size_t a = fastrange32(kLen, h32);
+  PREFETCH(data_ + a, 0, 3);
+  // Expand/remix with 64-bit golden ratio
+  uint64_t h = 0x9e3779b97f4a7c13ULL * h32;
+  for (unsigned i = 0;; ++i) {
+    // Two bit probes per uint64_t probe
+    uint64_t mask =
+        ((uint64_t)1 << (h & 63)) | ((uint64_t)1 << ((h >> 6) & 63));
+    or_func(&data_[a ^ i], mask);
+    if (i + 1 >= kNumDoubleProbes) {
+      return;
+    }
+    h = (h >> 12) | (h << 52);
+  }
+}
+
+}  // namespace ROCKSDB_NAMESPACE