From cd535c2280dea4c45b5138bce27870ff1c633d11 Mon Sep 17 00:00:00 2001
From: Kai Liu <kailiu@fb.com>
Date: Tue, 14 Jan 2014 21:30:13 -0800
Subject: [PATCH] Optimize MayContainHash()

Summary:
In latest leaf's, MayContainHash() consistently consumes 5%~7% CPU usage.

I checked the code and did an experiment with/without inlining this method.

In release mode, with `1024 * 1024 * 256` bits and `1024 * 512` entries, both call 2^30 MayContainHash() with distinctive parameters.

As the result showed, this patch reduced the running time from 9.127 sec to 7.891 sec.

Test Plan: make check

Reviewers: sdong, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15177
---
 util/dynamic_bloom.cc | 47 +++++++------------------------------------
 util/dynamic_bloom.h  | 33 +++++++++++++++++++++++++-----
 2 files changed, 35 insertions(+), 45 deletions(-)

diff --git a/util/dynamic_bloom.cc b/util/dynamic_bloom.cc
index 84f964d9e..94df660ef 100644
--- a/util/dynamic_bloom.cc
+++ b/util/dynamic_bloom.cc
@@ -20,50 +20,17 @@ DynamicBloom::DynamicBloom(uint32_t total_bits,
                            uint32_t (*hash_func)(const Slice& key),
                            uint32_t num_probes)
     : hash_func_(hash_func),
-      total_bits_((total_bits + 7) / 8 * 8),
-      num_probes_(num_probes) {
+      kTotalBits((total_bits + 7) / 8 * 8),
+      kNumProbes(num_probes) {
   assert(hash_func_);
-  assert(num_probes_ > 0);
-  assert(total_bits_ > 0);
-  data_.reset(new unsigned char[total_bits_ / 8]());
+  assert(kNumProbes > 0);
+  assert(kTotalBits > 0);
+  data_.reset(new unsigned char[kTotalBits / 8]());
 }
 
 DynamicBloom::DynamicBloom(uint32_t total_bits,
                            uint32_t num_probes)
-    : hash_func_(&BloomHash),
-      total_bits_((total_bits + 7) / 8 * 8),
-      num_probes_(num_probes) {
-  assert(num_probes_ > 0);
-  assert(total_bits_ > 0);
-  data_.reset(new unsigned char[total_bits_ / 8]());
+    : DynamicBloom(total_bits, &BloomHash, num_probes) {
 }
 
-void DynamicBloom::Add(const Slice& key) {
-  AddHash(hash_func_(key));
-}
-
-void DynamicBloom::AddHash(uint32_t h) {
-  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
-  for (uint32_t i = 0; i < num_probes_; i++) {
-    const uint32_t bitpos = h % total_bits_;
-    data_[bitpos/8] |= (1 << (bitpos % 8));
-    h += delta;
-  }
-}
-
-bool DynamicBloom::MayContain(const Slice& key) {
-  return (MayContainHash(hash_func_(key)));
-}
-
-bool DynamicBloom::MayContainHash(uint32_t h) {
-  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
-  for (uint32_t i = 0; i < num_probes_; i++) {
-    const uint32_t bitpos = h % total_bits_;
-    if ((data_[bitpos/8] & (1 << (bitpos % 8)))
-        == 0) return false;
-    h += delta;
-  }
-  return true;
-}
-
-}
+}  // rocksdb
diff --git a/util/dynamic_bloom.h b/util/dynamic_bloom.h
index aa29a4ae7..2b699dc77 100644
--- a/util/dynamic_bloom.h
+++ b/util/dynamic_bloom.h
@@ -13,9 +13,7 @@ namespace rocksdb {
 class Slice;
 
 class DynamicBloom {
-
  public:
-
   // total_bits: fixed total bits for the bloom
   // hash_func:  customized hash function
   // num_probes: number of hash probes for a single key
@@ -26,7 +24,7 @@ class DynamicBloom {
   explicit DynamicBloom(uint32_t total_bits, uint32_t num_probes = 6);
 
   // Assuming single threaded access to Add
-  void Add(const Slice& key);
+  void Add(const Slice& key) { AddHash(hash_func_(key)); }
 
   // Assuming single threaded access to Add
   void AddHash(uint32_t hash);
@@ -39,9 +37,34 @@ class DynamicBloom {
 
  private:
   uint32_t (*hash_func_)(const Slice& key);
-  uint32_t total_bits_;
-  uint32_t num_probes_;
+  const uint32_t kTotalBits;
+  const uint32_t kNumProbes;
   std::unique_ptr<unsigned char[]> data_;
 };
 
+inline bool DynamicBloom::MayContain(const Slice& key) {
+  return (MayContainHash(hash_func_(key)));
 }
+
+inline bool DynamicBloom::MayContainHash(uint32_t h) {
+  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+  for (uint32_t i = 0; i < kNumProbes; i++) {
+    const uint32_t bitpos = h % kTotalBits;
+    if (((data_[bitpos / 8]) & (1 << (bitpos % 8))) == 0) {
+      return false;
+    }
+    h += delta;
+  }
+  return true;
+}
+
+inline void DynamicBloom::AddHash(uint32_t h) {
+  const uint32_t delta = (h >> 17) | (h << 15);  // Rotate right 17 bits
+  for (uint32_t i = 0; i < kNumProbes; i++) {
+    const uint32_t bitpos = h % kTotalBits;
+    data_[bitpos / 8] |= (1 << (bitpos % 8));
+    h += delta;
+  }
+}
+
+}  // rocksdb