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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 | /* * Searching a VMA in the linear list task->mm->mmap is horribly slow. * Use an AVL (Adelson-Velskii and Landis) tree to speed up this search * from O(n) to O(log n), where n is the number of VMAs of the task * n is typically around 6, but may reach 3000 in some cases: object-oriented * databases, persistent store, generational garbage collection (Java, Lisp), * ElectricFence. * Written by Bruno Haible <haible@ma2s2.mathematik.uni-karlsruhe.de>. */ /* We keep the list and tree sorted by address. */ #define vm_avl_key vm_end #define vm_avl_key_t unsigned long /* typeof(vma->avl_key) */ /* * task->mm->mmap_avl is the AVL tree corresponding to task->mm->mmap * or, more exactly, its root. * A vm_area_struct has the following fields: * vm_avl_left left son of a tree node * vm_avl_right right son of a tree node * vm_avl_height 1+max(heightof(left),heightof(right)) * The empty tree is represented as NULL. */ /* Since the trees are balanced, their height will never be large. */ #define avl_maxheight 41 /* why this? a small exercise */ #define heightof(tree) ((tree) == vm_avl_empty ? 0 : (tree)->vm_avl_height) /* * Consistency and balancing rules: * 1. tree->vm_avl_height == 1+max(heightof(tree->vm_avl_left),heightof(tree->vm_avl_right)) * 2. abs( heightof(tree->vm_avl_left) - heightof(tree->vm_avl_right) ) <= 1 * 3. foreach node in tree->vm_avl_left: node->vm_avl_key <= tree->vm_avl_key, * foreach node in tree->vm_avl_right: node->vm_avl_key >= tree->vm_avl_key. */ #ifdef DEBUG_AVL /* Look up the nodes at the left and at the right of a given node. */ static void avl_neighbours (struct vm_area_struct * node, struct vm_area_struct * tree, struct vm_area_struct ** to_the_left, struct vm_area_struct ** to_the_right) { vm_avl_key_t key = node->vm_avl_key; *to_the_left = *to_the_right = NULL; for (;;) { if (tree == vm_avl_empty) { printk("avl_neighbours: node not found in the tree\n"); return; } if (key == tree->vm_avl_key) break; if (key < tree->vm_avl_key) { *to_the_right = tree; tree = tree->vm_avl_left; } else { *to_the_left = tree; tree = tree->vm_avl_right; } } if (tree != node) { printk("avl_neighbours: node not exactly found in the tree\n"); return; } if (tree->vm_avl_left != vm_avl_empty) { struct vm_area_struct * node; for (node = tree->vm_avl_left; node->vm_avl_right != vm_avl_empty; node = node->vm_avl_right) continue; *to_the_left = node; } if (tree->vm_avl_right != vm_avl_empty) { struct vm_area_struct * node; for (node = tree->vm_avl_right; node->vm_avl_left != vm_avl_empty; node = node->vm_avl_left) continue; *to_the_right = node; } if ((*to_the_left && ((*to_the_left)->vm_next != node)) || (node->vm_next != *to_the_right)) printk("avl_neighbours: tree inconsistent with list\n"); } #endif /* * Rebalance a tree. * After inserting or deleting a node of a tree we have a sequence of subtrees * nodes[0]..nodes[k-1] such that * nodes[0] is the root and nodes[i+1] = nodes[i]->{vm_avl_left|vm_avl_right}. */ static void avl_rebalance (struct vm_area_struct *** nodeplaces_ptr, int count) { for ( ; count > 0 ; count--) { struct vm_area_struct ** nodeplace = *--nodeplaces_ptr; struct vm_area_struct * node = *nodeplace; struct vm_area_struct * nodeleft = node->vm_avl_left; struct vm_area_struct * noderight = node->vm_avl_right; int heightleft = heightof(nodeleft); int heightright = heightof(noderight); if (heightright + 1 < heightleft) { /* */ /* * */ /* / \ */ /* n+2 n */ /* */ struct vm_area_struct * nodeleftleft = nodeleft->vm_avl_left; struct vm_area_struct * nodeleftright = nodeleft->vm_avl_right; int heightleftright = heightof(nodeleftright); if (heightof(nodeleftleft) >= heightleftright) { /* */ /* * n+2|n+3 */ /* / \ / \ */ /* n+2 n --> / n+1|n+2 */ /* / \ | / \ */ /* n+1 n|n+1 n+1 n|n+1 n */ /* */ node->vm_avl_left = nodeleftright; nodeleft->vm_avl_right = node; nodeleft->vm_avl_height = 1 + (node->vm_avl_height = 1 + heightleftright); *nodeplace = nodeleft; } else { /* */ /* * n+2 */ /* / \ / \ */ /* n+2 n --> n+1 n+1 */ /* / \ / \ / \ */ /* n n+1 n L R n */ /* / \ */ /* L R */ /* */ nodeleft->vm_avl_right = nodeleftright->vm_avl_left; node->vm_avl_left = nodeleftright->vm_avl_right; nodeleftright->vm_avl_left = nodeleft; nodeleftright->vm_avl_right = node; nodeleft->vm_avl_height = node->vm_avl_height = heightleftright; nodeleftright->vm_avl_height = heightleft; *nodeplace = nodeleftright; } } else if (heightleft + 1 < heightright) { /* similar to the above, just interchange 'left' <--> 'right' */ struct vm_area_struct * noderightright = noderight->vm_avl_right; struct vm_area_struct * noderightleft = noderight->vm_avl_left; int heightrightleft = heightof(noderightleft); if (heightof(noderightright) >= heightrightleft) { node->vm_avl_right = noderightleft; noderight->vm_avl_left = node; noderight->vm_avl_height = 1 + (node->vm_avl_height = 1 + heightrightleft); *nodeplace = noderight; } else { noderight->vm_avl_left = noderightleft->vm_avl_right; node->vm_avl_right = noderightleft->vm_avl_left; noderightleft->vm_avl_right = noderight; noderightleft->vm_avl_left = node; noderight->vm_avl_height = node->vm_avl_height = heightrightleft; noderightleft->vm_avl_height = heightright; *nodeplace = noderightleft; } } else { int height = (heightleft<heightright ? heightright : heightleft) + 1; if (height == node->vm_avl_height) break; node->vm_avl_height = height; } } } /* Insert a node into a tree. */ static inline void avl_insert (struct vm_area_struct * new_node, struct vm_area_struct ** ptree) { vm_avl_key_t key = new_node->vm_avl_key; struct vm_area_struct ** nodeplace = ptree; struct vm_area_struct ** stack[avl_maxheight]; int stack_count = 0; struct vm_area_struct *** stack_ptr = &stack[0]; /* = &stack[stackcount] */ for (;;) { struct vm_area_struct * node = *nodeplace; if (node == vm_avl_empty) break; *stack_ptr++ = nodeplace; stack_count++; if (key < node->vm_avl_key) nodeplace = &node->vm_avl_left; else nodeplace = &node->vm_avl_right; } new_node->vm_avl_left = vm_avl_empty; new_node->vm_avl_right = vm_avl_empty; new_node->vm_avl_height = 1; *nodeplace = new_node; avl_rebalance(stack_ptr,stack_count); } /* Insert a node into a tree, and * return the node to the left of it and the node to the right of it. */ static inline void avl_insert_neighbours (struct vm_area_struct * new_node, struct vm_area_struct ** ptree, struct vm_area_struct ** to_the_left, struct vm_area_struct ** to_the_right) { vm_avl_key_t key = new_node->vm_avl_key; struct vm_area_struct ** nodeplace = ptree; struct vm_area_struct ** stack[avl_maxheight]; int stack_count = 0; struct vm_area_struct *** stack_ptr = &stack[0]; /* = &stack[stackcount] */ *to_the_left = *to_the_right = NULL; for (;;) { struct vm_area_struct * node = *nodeplace; if (node == vm_avl_empty) break; *stack_ptr++ = nodeplace; stack_count++; if (key < node->vm_avl_key) { *to_the_right = node; nodeplace = &node->vm_avl_left; } else { *to_the_left = node; nodeplace = &node->vm_avl_right; } } new_node->vm_avl_left = vm_avl_empty; new_node->vm_avl_right = vm_avl_empty; new_node->vm_avl_height = 1; *nodeplace = new_node; avl_rebalance(stack_ptr,stack_count); } /* Removes a node out of a tree. */ static void avl_remove (struct vm_area_struct * node_to_delete, struct vm_area_struct ** ptree) { vm_avl_key_t key = node_to_delete->vm_avl_key; struct vm_area_struct ** nodeplace = ptree; struct vm_area_struct ** stack[avl_maxheight]; int stack_count = 0; struct vm_area_struct *** stack_ptr = &stack[0]; /* = &stack[stackcount] */ struct vm_area_struct ** nodeplace_to_delete; for (;;) { struct vm_area_struct * node = *nodeplace; #ifdef DEBUG_AVL if (node == vm_avl_empty) { /* what? node_to_delete not found in tree? */ printk("avl_remove: node to delete not found in tree\n"); return; } #endif *stack_ptr++ = nodeplace; stack_count++; if (key == node->vm_avl_key) break; if (key < node->vm_avl_key) nodeplace = &node->vm_avl_left; else nodeplace = &node->vm_avl_right; } nodeplace_to_delete = nodeplace; /* Have to remove node_to_delete = *nodeplace_to_delete. */ if (node_to_delete->vm_avl_left == vm_avl_empty) { *nodeplace_to_delete = node_to_delete->vm_avl_right; stack_ptr--; stack_count--; } else { struct vm_area_struct *** stack_ptr_to_delete = stack_ptr; struct vm_area_struct ** nodeplace = &node_to_delete->vm_avl_left; struct vm_area_struct * node; for (;;) { node = *nodeplace; if (node->vm_avl_right == vm_avl_empty) break; *stack_ptr++ = nodeplace; stack_count++; nodeplace = &node->vm_avl_right; } *nodeplace = node->vm_avl_left; /* node replaces node_to_delete */ node->vm_avl_left = node_to_delete->vm_avl_left; node->vm_avl_right = node_to_delete->vm_avl_right; node->vm_avl_height = node_to_delete->vm_avl_height; *nodeplace_to_delete = node; /* replace node_to_delete */ *stack_ptr_to_delete = &node->vm_avl_left; /* replace &node_to_delete->vm_avl_left */ } avl_rebalance(stack_ptr,stack_count); } #ifdef DEBUG_AVL /* print a list */ static void printk_list (struct vm_area_struct * vma) { printk("["); while (vma) { printk("%08lX-%08lX", vma->vm_start, vma->vm_end); vma = vma->vm_next; if (!vma) break; printk(" "); } printk("]"); } /* print a tree */ static void printk_avl (struct vm_area_struct * tree) { if (tree != vm_avl_empty) { printk("("); if (tree->vm_avl_left != vm_avl_empty) { printk_avl(tree->vm_avl_left); printk("<"); } printk("%08lX-%08lX", tree->vm_start, tree->vm_end); if (tree->vm_avl_right != vm_avl_empty) { printk(">"); printk_avl(tree->vm_avl_right); } printk(")"); } } static char *avl_check_point = "somewhere"; /* check a tree's consistency and balancing */ static void avl_checkheights (struct vm_area_struct * tree) { int h, hl, hr; if (tree == vm_avl_empty) return; avl_checkheights(tree->vm_avl_left); avl_checkheights(tree->vm_avl_right); h = tree->vm_avl_height; hl = heightof(tree->vm_avl_left); hr = heightof(tree->vm_avl_right); if ((h == hl+1) && (hr <= hl) && (hl <= hr+1)) return; if ((h == hr+1) && (hl <= hr) && (hr <= hl+1)) return; printk("%s: avl_checkheights: heights inconsistent\n",avl_check_point); } /* check that all values stored in a tree are < key */ static void avl_checkleft (struct vm_area_struct * tree, vm_avl_key_t key) { if (tree == vm_avl_empty) return; avl_checkleft(tree->vm_avl_left,key); avl_checkleft(tree->vm_avl_right,key); if (tree->vm_avl_key < key) return; printk("%s: avl_checkleft: left key %lu >= top key %lu\n",avl_check_point,tree->vm_avl_key,key); } /* check that all values stored in a tree are > key */ static void avl_checkright (struct vm_area_struct * tree, vm_avl_key_t key) { if (tree == vm_avl_empty) return; avl_checkright(tree->vm_avl_left,key); avl_checkright(tree->vm_avl_right,key); if (tree->vm_avl_key > key) return; printk("%s: avl_checkright: right key %lu <= top key %lu\n",avl_check_point,tree->vm_avl_key,key); } /* check that all values are properly increasing */ static void avl_checkorder (struct vm_area_struct * tree) { if (tree == vm_avl_empty) return; avl_checkorder(tree->vm_avl_left); avl_checkorder(tree->vm_avl_right); avl_checkleft(tree->vm_avl_left,tree->vm_avl_key); avl_checkright(tree->vm_avl_right,tree->vm_avl_key); } /* all checks */ static void avl_check (struct task_struct * task, char *caller) { avl_check_point = caller; /* printk("task \"%s\", %s\n",task->comm,caller); */ /* printk("task \"%s\" list: ",task->comm); printk_list(task->mm->mmap); printk("\n"); */ /* printk("task \"%s\" tree: ",task->comm); printk_avl(task->mm->mmap_avl); printk("\n"); */ avl_checkheights(task->mm->mmap_avl); avl_checkorder(task->mm->mmap_avl); } #endif |