wtf/TCPageMap.h

   1 // Copyright (c) 2005, Google Inc.
   2 // All rights reserved.
   3 //
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   9 // notice, this list of conditions and the following disclaimer.
  10 //     * Redistributions in binary form must reproduce the above
  11 // copyright notice, this list of conditions and the following disclaimer
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  16 // this software without specific prior written permission.
  17 //
  18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29
  30 // ---
  31 // Author: Sanjay Ghemawat <opensource@google.com>
  32 //
  33 // A data structure used by the caching malloc.  It maps from page# to
  34 // a pointer that contains info about that page.  We use two
  35 // representations: one for 32-bit addresses, and another for 64 bit
  36 // addresses.  Both representations provide the same interface.  The
  37 // first representation is implemented as a flat array, the seconds as
  38 // a three-level radix tree that strips away approximately 1/3rd of
  39 // the bits every time.
  40 //
  41 // The BITS parameter should be the number of bits required to hold
  42 // a page number.  E.g., with 32 bit pointers and 4K pages (i.e.,
  43 // page offset fits in lower 12 bits), BITS == 20.
  44
  45 #ifndef TCMALLOC_PAGEMAP_H__
  46 #define TCMALLOC_PAGEMAP_H__
  47
  48 #if HAVE(STDINT_H)
  49 #include <stdint.h>
  50 #elif HAVE(INTTYPES_H)
  51 #include <inttypes.h>
  52 #else
  53 #include <sys/types.h>
  54 #endif
  55
  56 #include <string.h>
  57
  58 #include "Assertions.h"
  59
  60 // Single-level array
  61 template <int BITS>
  62 class TCMalloc_PageMap1 {
  63  private:
  64   void** array_;
  65
  66  public:
  67   typedef uintptr_t Number;
  68
  69   void init(void* (*allocator)(size_t)) {
  70     array_ = reinterpret_cast<void**>((*allocator)(sizeof(void*) << BITS));
  71     memset(array_, 0, sizeof(void*) << BITS);
  72   }
  73
  74   // Ensure that the map contains initialized entries "x .. x+n-1".
  75   // Returns true if successful, false if we could not allocate memory.
  76   bool Ensure(Number x, size_t n) {
  77     // Nothing to do since flat array was allocate at start
  78     return true;
  79   }
  80
  81   void PreallocateMoreMemory() {}
  82
  83   // REQUIRES "k" is in range "[0,2^BITS-1]".
  84   // REQUIRES "k" has been ensured before.
  85   //
  86   // Return the current value for KEY.  Returns "Value()" if not
  87   // yet set.
  88   void* get(Number k) const {
  89     return array_[k];
  90   }
  91
  92   // REQUIRES "k" is in range "[0,2^BITS-1]".
  93   // REQUIRES "k" has been ensured before.
  94   //
  95   // Sets the value for KEY.
  96   void set(Number k, void* v) {
  97     array_[k] = v;
  98   }
  99 };
 100
 101 // Two-level radix tree
 102 template <int BITS>
 103 class TCMalloc_PageMap2 {
 104  private:
 105   // Put 32 entries in the root and (2^BITS)/32 entries in each leaf.
 106   static const int ROOT_BITS = 5;
 107   static const int ROOT_LENGTH = 1 << ROOT_BITS;
 108
 109   static const int LEAF_BITS = BITS - ROOT_BITS;
 110   static const int LEAF_LENGTH = 1 << LEAF_BITS;
 111
 112   // Leaf node
 113   struct Leaf {
 114     void* values[LEAF_LENGTH];
 115   };
 116
 117   Leaf* root_[ROOT_LENGTH];             // Pointers to 32 child nodes
 118   void* (*allocator_)(size_t);          // Memory allocator
 119
 120  public:
 121   typedef uintptr_t Number;
 122
 123   void init(void* (*allocator)(size_t)) {
 124     allocator_ = allocator;
 125     memset(root_, 0, sizeof(root_));
 126   }
 127
 128   void* get(Number k) const {
 129     ASSERT(k >> BITS == 0);
 130     const Number i1 = k >> LEAF_BITS;
 131     const Number i2 = k & (LEAF_LENGTH-1);
 132     return root_[i1]->values[i2];
 133   }
 134
 135   void set(Number k, void* v) {
 136     ASSERT(k >> BITS == 0);
 137     const Number i1 = k >> LEAF_BITS;
 138     const Number i2 = k & (LEAF_LENGTH-1);
 139     root_[i1]->values[i2] = v;
 140   }
 141
 142   bool Ensure(Number start, size_t n) {
 143     for (Number key = start; key <= start + n - 1; ) {
 144       const Number i1 = key >> LEAF_BITS;
 145
 146       // Make 2nd level node if necessary
 147       if (root_[i1] == NULL) {
 148         Leaf* leaf = reinterpret_cast<Leaf*>((*allocator_)(sizeof(Leaf)));
 149         if (leaf == NULL) return false;
 150         memset(leaf, 0, sizeof(*leaf));
 151         root_[i1] = leaf;
 152       }
 153
 154       // Advance key past whatever is covered by this leaf node
 155       key = ((key >> LEAF_BITS) + 1) << LEAF_BITS;
 156     }
 157     return true;
 158   }
 159
 160   void PreallocateMoreMemory() {
 161     // Allocate enough to keep track of all possible pages
 162     Ensure(0, 1 << BITS);
 163   }
 164
 165 #ifdef WTF_CHANGES
 166   template<class Visitor, class MemoryReader>
 167   void visit(const Visitor& visitor, const MemoryReader& reader)
 168   {
 169     for (int i = 0; i < ROOT_LENGTH; i++) {
 170       if (!root_[i])
 171         continue;
 172
 173       Leaf* l = reader(reinterpret_cast<Leaf*>(root_[i]));
 174       for (int j = 0; j < LEAF_LENGTH; j += visitor.visit(l->values[j]))
 175         ;
 176     }
 177   }
 178 #endif
 179 };
 180
 181 // Three-level radix tree
 182 template <int BITS>
 183 class TCMalloc_PageMap3 {
 184  private:
 185   // How many bits should we consume at each interior level
 186   static const int INTERIOR_BITS = (BITS + 2) / 3; // Round-up
 187   static const int INTERIOR_LENGTH = 1 << INTERIOR_BITS;
 188
 189   // How many bits should we consume at leaf level
 190   static const int LEAF_BITS = BITS - 2*INTERIOR_BITS;
 191   static const int LEAF_LENGTH = 1 << LEAF_BITS;
 192
 193   // Interior node
 194   struct Node {
 195     Node* ptrs[INTERIOR_LENGTH];
 196   };
 197
 198   // Leaf node
 199   struct Leaf {
 200     void* values[LEAF_LENGTH];
 201   };
 202
 203   Node* root_;                          // Root of radix tree
 204   void* (*allocator_)(size_t);          // Memory allocator
 205
 206   Node* NewNode() {
 207     Node* result = reinterpret_cast<Node*>((*allocator_)(sizeof(Node)));
 208     if (result != NULL) {
 209       memset(result, 0, sizeof(*result));
 210     }
 211     return result;
 212   }
 213
 214  public:
 215   typedef uintptr_t Number;
 216
 217   void init(void* (*allocator)(size_t)) {
 218     allocator_ = allocator;
 219     root_ = NewNode();
 220   }
 221
 222   void* get(Number k) const {
 223     ASSERT(k >> BITS == 0);
 224     const Number i1 = k >> (LEAF_BITS + INTERIOR_BITS);
 225     const Number i2 = (k >> LEAF_BITS) & (INTERIOR_LENGTH-1);
 226     const Number i3 = k & (LEAF_LENGTH-1);
 227     return reinterpret_cast<Leaf*>(root_->ptrs[i1]->ptrs[i2])->values[i3];
 228   }
 229
 230   void set(Number k, void* v) {
 231     ASSERT(k >> BITS == 0);
 232     const Number i1 = k >> (LEAF_BITS + INTERIOR_BITS);
 233     const Number i2 = (k >> LEAF_BITS) & (INTERIOR_LENGTH-1);
 234     const Number i3 = k & (LEAF_LENGTH-1);
 235     reinterpret_cast<Leaf*>(root_->ptrs[i1]->ptrs[i2])->values[i3] = v;
 236   }
 237
 238   bool Ensure(Number start, size_t n) {
 239     for (Number key = start; key <= start + n - 1; ) {
 240       const Number i1 = key >> (LEAF_BITS + INTERIOR_BITS);
 241       const Number i2 = (key >> LEAF_BITS) & (INTERIOR_LENGTH-1);
 242
 243       // Make 2nd level node if necessary
 244       if (root_->ptrs[i1] == NULL) {
 245         Node* n = NewNode();
 246         if (n == NULL) return false;
 247         root_->ptrs[i1] = n;
 248       }
 249
 250       // Make leaf node if necessary
 251       if (root_->ptrs[i1]->ptrs[i2] == NULL) {
 252         Leaf* leaf = reinterpret_cast<Leaf*>((*allocator_)(sizeof(Leaf)));
 253         if (leaf == NULL) return false;
 254         memset(leaf, 0, sizeof(*leaf));
 255         root_->ptrs[i1]->ptrs[i2] = reinterpret_cast<Node*>(leaf);
 256       }
 257
 258       // Advance key past whatever is covered by this leaf node
 259       key = ((key >> LEAF_BITS) + 1) << LEAF_BITS;
 260     }
 261     return true;
 262   }
 263
 264   void PreallocateMoreMemory() {
 265   }
 266
 267 #ifdef WTF_CHANGES
 268   template<class Visitor, class MemoryReader>
 269   void visit(const Visitor& visitor, const MemoryReader& reader) {
 270     Node* root = reader(root_);
 271     for (int i = 0; i < INTERIOR_LENGTH; i++) {
 272       if (!root->ptrs[i])
 273         continue;
 274
 275       Node* n = reader(root->ptrs[i]);
 276       for (int j = 0; j < INTERIOR_LENGTH; j++) {
 277         if (!n->ptrs[j])
 278           continue;
 279
 280         Leaf* l = reader(reinterpret_cast<Leaf*>(n->ptrs[j]));
 281         for (int k = 0; k < LEAF_LENGTH; k += visitor.visit(l->values[k]))
 282           ;
 283       }
 284     }
 285   }
 286 #endif
 287 };
 288
 289 #endif  // TCMALLOC_PAGEMAP_H__