1 /* cpumap.c: used for optimizing CPU assignment
2 *
3 * Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com>
4 */
5
6 #include <linux/module.h>
7 #include <linux/slab.h>
8 #include <linux/kernel.h>
9 #include <linux/init.h>
10 #include <linux/cpumask.h>
11 #include <linux/spinlock.h>
12 #include <asm/cpudata.h>
13 #include "cpumap.h"
14
15
16 enum {
17 CPUINFO_LVL_ROOT = 0,
18 CPUINFO_LVL_NODE,
19 CPUINFO_LVL_CORE,
20 CPUINFO_LVL_PROC,
21 CPUINFO_LVL_MAX,
22 };
23
24 enum {
25 ROVER_NO_OP = 0,
26 /* Increment rover every time level is visited */
27 ROVER_INC_ON_VISIT = 1 << 0,
28 /* Increment parent's rover every time rover wraps around */
29 ROVER_INC_PARENT_ON_LOOP = 1 << 1,
30 };
31
32 struct cpuinfo_node {
33 int id;
34 int level;
35 int num_cpus; /* Number of CPUs in this hierarchy */
36 int parent_index;
37 int child_start; /* Array index of the first child node */
38 int child_end; /* Array index of the last child node */
39 int rover; /* Child node iterator */
40 };
41
42 struct cpuinfo_level {
43 int start_index; /* Index of first node of a level in a cpuinfo tree */
44 int end_index; /* Index of last node of a level in a cpuinfo tree */
45 int num_nodes; /* Number of nodes in a level in a cpuinfo tree */
46 };
47
48 struct cpuinfo_tree {
49 int total_nodes;
50
51 /* Offsets into nodes[] for each level of the tree */
52 struct cpuinfo_level level[CPUINFO_LVL_MAX];
53 struct cpuinfo_node nodes[0];
54 };
55
56
57 static struct cpuinfo_tree *cpuinfo_tree;
58
59 static u16 cpu_distribution_map[NR_CPUS];
60 static DEFINE_SPINLOCK(cpu_map_lock);
61
62
63 /* Niagara optimized cpuinfo tree traversal. */
64 static const int niagara_iterate_method[] = {
65 [CPUINFO_LVL_ROOT] = ROVER_NO_OP,
66
67 /* Strands (or virtual CPUs) within a core may not run concurrently
68 * on the Niagara, as instruction pipeline(s) are shared. Distribute
69 * work to strands in different cores first for better concurrency.
70 * Go to next NUMA node when all cores are used.
71 */
72 [CPUINFO_LVL_NODE] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,
73
74 /* Strands are grouped together by proc_id in cpuinfo_sparc, i.e.
75 * a proc_id represents an instruction pipeline. Distribute work to
76 * strands in different proc_id groups if the core has multiple
77 * instruction pipelines (e.g. the Niagara 2/2+ has two).
78 */
79 [CPUINFO_LVL_CORE] = ROVER_INC_ON_VISIT,
80
81 /* Pick the next strand in the proc_id group. */
82 [CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT,
83 };
84
85 /* Generic cpuinfo tree traversal. Distribute work round robin across NUMA
86 * nodes.
87 */
88 static const int generic_iterate_method[] = {
89 [CPUINFO_LVL_ROOT] = ROVER_INC_ON_VISIT,
90 [CPUINFO_LVL_NODE] = ROVER_NO_OP,
91 [CPUINFO_LVL_CORE] = ROVER_INC_PARENT_ON_LOOP,
92 [CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,
93 };
94
95
cpuinfo_id(int cpu,int level)96 static int cpuinfo_id(int cpu, int level)
97 {
98 int id;
99
100 switch (level) {
101 case CPUINFO_LVL_ROOT:
102 id = 0;
103 break;
104 case CPUINFO_LVL_NODE:
105 id = cpu_to_node(cpu);
106 break;
107 case CPUINFO_LVL_CORE:
108 id = cpu_data(cpu).core_id;
109 break;
110 case CPUINFO_LVL_PROC:
111 id = cpu_data(cpu).proc_id;
112 break;
113 default:
114 id = -EINVAL;
115 }
116 return id;
117 }
118
119 /*
120 * Enumerate the CPU information in __cpu_data to determine the start index,
121 * end index, and number of nodes for each level in the cpuinfo tree. The
122 * total number of cpuinfo nodes required to build the tree is returned.
123 */
enumerate_cpuinfo_nodes(struct cpuinfo_level * tree_level)124 static int enumerate_cpuinfo_nodes(struct cpuinfo_level *tree_level)
125 {
126 int prev_id[CPUINFO_LVL_MAX];
127 int i, n, num_nodes;
128
129 for (i = CPUINFO_LVL_ROOT; i < CPUINFO_LVL_MAX; i++) {
130 struct cpuinfo_level *lv = &tree_level[i];
131
132 prev_id[i] = -1;
133 lv->start_index = lv->end_index = lv->num_nodes = 0;
134 }
135
136 num_nodes = 1; /* Include the root node */
137
138 for (i = 0; i < num_possible_cpus(); i++) {
139 if (!cpu_online(i))
140 continue;
141
142 n = cpuinfo_id(i, CPUINFO_LVL_NODE);
143 if (n > prev_id[CPUINFO_LVL_NODE]) {
144 tree_level[CPUINFO_LVL_NODE].num_nodes++;
145 prev_id[CPUINFO_LVL_NODE] = n;
146 num_nodes++;
147 }
148 n = cpuinfo_id(i, CPUINFO_LVL_CORE);
149 if (n > prev_id[CPUINFO_LVL_CORE]) {
150 tree_level[CPUINFO_LVL_CORE].num_nodes++;
151 prev_id[CPUINFO_LVL_CORE] = n;
152 num_nodes++;
153 }
154 n = cpuinfo_id(i, CPUINFO_LVL_PROC);
155 if (n > prev_id[CPUINFO_LVL_PROC]) {
156 tree_level[CPUINFO_LVL_PROC].num_nodes++;
157 prev_id[CPUINFO_LVL_PROC] = n;
158 num_nodes++;
159 }
160 }
161
162 tree_level[CPUINFO_LVL_ROOT].num_nodes = 1;
163
164 n = tree_level[CPUINFO_LVL_NODE].num_nodes;
165 tree_level[CPUINFO_LVL_NODE].start_index = 1;
166 tree_level[CPUINFO_LVL_NODE].end_index = n;
167
168 n++;
169 tree_level[CPUINFO_LVL_CORE].start_index = n;
170 n += tree_level[CPUINFO_LVL_CORE].num_nodes;
171 tree_level[CPUINFO_LVL_CORE].end_index = n - 1;
172
173 tree_level[CPUINFO_LVL_PROC].start_index = n;
174 n += tree_level[CPUINFO_LVL_PROC].num_nodes;
175 tree_level[CPUINFO_LVL_PROC].end_index = n - 1;
176
177 return num_nodes;
178 }
179
180 /* Build a tree representation of the CPU hierarchy using the per CPU
181 * information in __cpu_data. Entries in __cpu_data[0..NR_CPUS] are
182 * assumed to be sorted in ascending order based on node, core_id, and
183 * proc_id (in order of significance).
184 */
build_cpuinfo_tree(void)185 static struct cpuinfo_tree *build_cpuinfo_tree(void)
186 {
187 struct cpuinfo_tree *new_tree;
188 struct cpuinfo_node *node;
189 struct cpuinfo_level tmp_level[CPUINFO_LVL_MAX];
190 int num_cpus[CPUINFO_LVL_MAX];
191 int level_rover[CPUINFO_LVL_MAX];
192 int prev_id[CPUINFO_LVL_MAX];
193 int n, id, cpu, prev_cpu, last_cpu, level;
194
195 n = enumerate_cpuinfo_nodes(tmp_level);
196
197 new_tree = kzalloc(sizeof(struct cpuinfo_tree) +
198 (sizeof(struct cpuinfo_node) * n), GFP_ATOMIC);
199 if (!new_tree)
200 return NULL;
201
202 new_tree->total_nodes = n;
203 memcpy(&new_tree->level, tmp_level, sizeof(tmp_level));
204
205 prev_cpu = cpu = first_cpu(cpu_online_map);
206
207 /* Initialize all levels in the tree with the first CPU */
208 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; level--) {
209 n = new_tree->level[level].start_index;
210
211 level_rover[level] = n;
212 node = &new_tree->nodes[n];
213
214 id = cpuinfo_id(cpu, level);
215 if (unlikely(id < 0)) {
216 kfree(new_tree);
217 return NULL;
218 }
219 node->id = id;
220 node->level = level;
221 node->num_cpus = 1;
222
223 node->parent_index = (level > CPUINFO_LVL_ROOT)
224 ? new_tree->level[level - 1].start_index : -1;
225
226 node->child_start = node->child_end = node->rover =
227 (level == CPUINFO_LVL_PROC)
228 ? cpu : new_tree->level[level + 1].start_index;
229
230 prev_id[level] = node->id;
231 num_cpus[level] = 1;
232 }
233
234 for (last_cpu = (num_possible_cpus() - 1); last_cpu >= 0; last_cpu--) {
235 if (cpu_online(last_cpu))
236 break;
237 }
238
239 while (++cpu <= last_cpu) {
240 if (!cpu_online(cpu))
241 continue;
242
243 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT;
244 level--) {
245 id = cpuinfo_id(cpu, level);
246 if (unlikely(id < 0)) {
247 kfree(new_tree);
248 return NULL;
249 }
250
251 if ((id != prev_id[level]) || (cpu == last_cpu)) {
252 prev_id[level] = id;
253 node = &new_tree->nodes[level_rover[level]];
254 node->num_cpus = num_cpus[level];
255 num_cpus[level] = 1;
256
257 if (cpu == last_cpu)
258 node->num_cpus++;
259
260 /* Connect tree node to parent */
261 if (level == CPUINFO_LVL_ROOT)
262 node->parent_index = -1;
263 else
264 node->parent_index =
265 level_rover[level - 1];
266
267 if (level == CPUINFO_LVL_PROC) {
268 node->child_end =
269 (cpu == last_cpu) ? cpu : prev_cpu;
270 } else {
271 node->child_end =
272 level_rover[level + 1] - 1;
273 }
274
275 /* Initialize the next node in the same level */
276 n = ++level_rover[level];
277 if (n <= new_tree->level[level].end_index) {
278 node = &new_tree->nodes[n];
279 node->id = id;
280 node->level = level;
281
282 /* Connect node to child */
283 node->child_start = node->child_end =
284 node->rover =
285 (level == CPUINFO_LVL_PROC)
286 ? cpu : level_rover[level + 1];
287 }
288 } else
289 num_cpus[level]++;
290 }
291 prev_cpu = cpu;
292 }
293
294 return new_tree;
295 }
296
increment_rover(struct cpuinfo_tree * t,int node_index,int root_index,const int * rover_inc_table)297 static void increment_rover(struct cpuinfo_tree *t, int node_index,
298 int root_index, const int *rover_inc_table)
299 {
300 struct cpuinfo_node *node = &t->nodes[node_index];
301 int top_level, level;
302
303 top_level = t->nodes[root_index].level;
304 for (level = node->level; level >= top_level; level--) {
305 node->rover++;
306 if (node->rover <= node->child_end)
307 return;
308
309 node->rover = node->child_start;
310 /* If parent's rover does not need to be adjusted, stop here. */
311 if ((level == top_level) ||
312 !(rover_inc_table[level] & ROVER_INC_PARENT_ON_LOOP))
313 return;
314
315 node = &t->nodes[node->parent_index];
316 }
317 }
318
iterate_cpu(struct cpuinfo_tree * t,unsigned int root_index)319 static int iterate_cpu(struct cpuinfo_tree *t, unsigned int root_index)
320 {
321 const int *rover_inc_table;
322 int level, new_index, index = root_index;
323
324 switch (sun4v_chip_type) {
325 case SUN4V_CHIP_NIAGARA1:
326 case SUN4V_CHIP_NIAGARA2:
327 rover_inc_table = niagara_iterate_method;
328 break;
329 default:
330 rover_inc_table = generic_iterate_method;
331 }
332
333 for (level = t->nodes[root_index].level; level < CPUINFO_LVL_MAX;
334 level++) {
335 new_index = t->nodes[index].rover;
336 if (rover_inc_table[level] & ROVER_INC_ON_VISIT)
337 increment_rover(t, index, root_index, rover_inc_table);
338
339 index = new_index;
340 }
341 return index;
342 }
343
_cpu_map_rebuild(void)344 static void _cpu_map_rebuild(void)
345 {
346 int i;
347
348 if (cpuinfo_tree) {
349 kfree(cpuinfo_tree);
350 cpuinfo_tree = NULL;
351 }
352
353 cpuinfo_tree = build_cpuinfo_tree();
354 if (!cpuinfo_tree)
355 return;
356
357 /* Build CPU distribution map that spans all online CPUs. No need
358 * to check if the CPU is online, as that is done when the cpuinfo
359 * tree is being built.
360 */
361 for (i = 0; i < cpuinfo_tree->nodes[0].num_cpus; i++)
362 cpu_distribution_map[i] = iterate_cpu(cpuinfo_tree, 0);
363 }
364
365 /* Fallback if the cpuinfo tree could not be built. CPU mapping is linear
366 * round robin.
367 */
simple_map_to_cpu(unsigned int index)368 static int simple_map_to_cpu(unsigned int index)
369 {
370 int i, end, cpu_rover;
371
372 cpu_rover = 0;
373 end = index % num_online_cpus();
374 for (i = 0; i < num_possible_cpus(); i++) {
375 if (cpu_online(cpu_rover)) {
376 if (cpu_rover >= end)
377 return cpu_rover;
378
379 cpu_rover++;
380 }
381 }
382
383 /* Impossible, since num_online_cpus() <= num_possible_cpus() */
384 return first_cpu(cpu_online_map);
385 }
386
_map_to_cpu(unsigned int index)387 static int _map_to_cpu(unsigned int index)
388 {
389 struct cpuinfo_node *root_node;
390
391 if (unlikely(!cpuinfo_tree)) {
392 _cpu_map_rebuild();
393 if (!cpuinfo_tree)
394 return simple_map_to_cpu(index);
395 }
396
397 root_node = &cpuinfo_tree->nodes[0];
398 #ifdef CONFIG_HOTPLUG_CPU
399 if (unlikely(root_node->num_cpus != num_online_cpus())) {
400 _cpu_map_rebuild();
401 if (!cpuinfo_tree)
402 return simple_map_to_cpu(index);
403 }
404 #endif
405 return cpu_distribution_map[index % root_node->num_cpus];
406 }
407
map_to_cpu(unsigned int index)408 int map_to_cpu(unsigned int index)
409 {
410 int mapped_cpu;
411 unsigned long flag;
412
413 spin_lock_irqsave(&cpu_map_lock, flag);
414 mapped_cpu = _map_to_cpu(index);
415
416 #ifdef CONFIG_HOTPLUG_CPU
417 while (unlikely(!cpu_online(mapped_cpu)))
418 mapped_cpu = _map_to_cpu(index);
419 #endif
420 spin_unlock_irqrestore(&cpu_map_lock, flag);
421 return mapped_cpu;
422 }
423 EXPORT_SYMBOL(map_to_cpu);
424
cpu_map_rebuild(void)425 void cpu_map_rebuild(void)
426 {
427 unsigned long flag;
428
429 spin_lock_irqsave(&cpu_map_lock, flag);
430 _cpu_map_rebuild();
431 spin_unlock_irqrestore(&cpu_map_lock, flag);
432 }
433