1// SPDX-License-Identifier: GPL-2.0
2/* cpumap.c: used for optimizing CPU assignment
3 *
4 * Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com>
5 */
6
7#include <linux/export.h>
8#include <linux/slab.h>
9#include <linux/kernel.h>
10#include <linux/cpumask.h>
11#include <linux/spinlock.h>
12#include <asm/cpudata.h>
13#include "cpumap.h"
14
15
16enum {
17 CPUINFO_LVL_ROOT = 0,
18 CPUINFO_LVL_NODE,
19 CPUINFO_LVL_CORE,
20 CPUINFO_LVL_PROC,
21 CPUINFO_LVL_MAX,
22};
23
24enum {
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
32struct 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
42struct 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
48struct 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[] __counted_by(total_nodes);
54};
55
56
57static struct cpuinfo_tree *cpuinfo_tree;
58
59static u16 cpu_distribution_map[NR_CPUS];
60static DEFINE_SPINLOCK(cpu_map_lock);
61
62
63/* Niagara optimized cpuinfo tree traversal. */
64static 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 */
88static 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
96static 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 */
124static 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(cpu: i))
140 continue;
141
142 n = cpuinfo_id(cpu: i, level: 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(cpu: i, level: 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(cpu: i, level: 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 */
185static 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(tree_level: tmp_level);
196
197 new_tree = kzalloc(struct_size(new_tree, nodes, n), GFP_ATOMIC);
198 if (!new_tree)
199 return NULL;
200
201 new_tree->total_nodes = n;
202 memcpy(&new_tree->level, tmp_level, sizeof(tmp_level));
203
204 prev_cpu = cpu = cpumask_first(cpu_online_mask);
205
206 /* Initialize all levels in the tree with the first CPU */
207 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; level--) {
208 n = new_tree->level[level].start_index;
209
210 level_rover[level] = n;
211 node = &new_tree->nodes[n];
212
213 id = cpuinfo_id(cpu, level);
214 if (unlikely(id < 0)) {
215 kfree(objp: new_tree);
216 return NULL;
217 }
218 node->id = id;
219 node->level = level;
220 node->num_cpus = 1;
221
222 node->parent_index = (level > CPUINFO_LVL_ROOT)
223 ? new_tree->level[level - 1].start_index : -1;
224
225 node->child_start = node->child_end = node->rover =
226 (level == CPUINFO_LVL_PROC)
227 ? cpu : new_tree->level[level + 1].start_index;
228
229 prev_id[level] = node->id;
230 num_cpus[level] = 1;
231 }
232
233 for (last_cpu = (num_possible_cpus() - 1); last_cpu >= 0; last_cpu--) {
234 if (cpu_online(cpu: last_cpu))
235 break;
236 }
237
238 while (++cpu <= last_cpu) {
239 if (!cpu_online(cpu))
240 continue;
241
242 for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT;
243 level--) {
244 id = cpuinfo_id(cpu, level);
245 if (unlikely(id < 0)) {
246 kfree(objp: new_tree);
247 return NULL;
248 }
249
250 if ((id != prev_id[level]) || (cpu == last_cpu)) {
251 prev_id[level] = id;
252 node = &new_tree->nodes[level_rover[level]];
253 node->num_cpus = num_cpus[level];
254 num_cpus[level] = 1;
255
256 if (cpu == last_cpu)
257 node->num_cpus++;
258
259 /* Connect tree node to parent */
260 if (level == CPUINFO_LVL_ROOT)
261 node->parent_index = -1;
262 else
263 node->parent_index =
264 level_rover[level - 1];
265
266 if (level == CPUINFO_LVL_PROC) {
267 node->child_end =
268 (cpu == last_cpu) ? cpu : prev_cpu;
269 } else {
270 node->child_end =
271 level_rover[level + 1] - 1;
272 }
273
274 /* Initialize the next node in the same level */
275 n = ++level_rover[level];
276 if (n <= new_tree->level[level].end_index) {
277 node = &new_tree->nodes[n];
278 node->id = id;
279 node->level = level;
280
281 /* Connect node to child */
282 node->child_start = node->child_end =
283 node->rover =
284 (level == CPUINFO_LVL_PROC)
285 ? cpu : level_rover[level + 1];
286 }
287 } else
288 num_cpus[level]++;
289 }
290 prev_cpu = cpu;
291 }
292
293 return new_tree;
294}
295
296static void increment_rover(struct cpuinfo_tree *t, int node_index,
297 int root_index, const int *rover_inc_table)
298{
299 struct cpuinfo_node *node = &t->nodes[node_index];
300 int top_level, level;
301
302 top_level = t->nodes[root_index].level;
303 for (level = node->level; level >= top_level; level--) {
304 node->rover++;
305 if (node->rover <= node->child_end)
306 return;
307
308 node->rover = node->child_start;
309 /* If parent's rover does not need to be adjusted, stop here. */
310 if ((level == top_level) ||
311 !(rover_inc_table[level] & ROVER_INC_PARENT_ON_LOOP))
312 return;
313
314 node = &t->nodes[node->parent_index];
315 }
316}
317
318static int iterate_cpu(struct cpuinfo_tree *t, unsigned int root_index)
319{
320 const int *rover_inc_table;
321 int level, new_index, index = root_index;
322
323 switch (sun4v_chip_type) {
324 case SUN4V_CHIP_NIAGARA1:
325 case SUN4V_CHIP_NIAGARA2:
326 case SUN4V_CHIP_NIAGARA3:
327 case SUN4V_CHIP_NIAGARA4:
328 case SUN4V_CHIP_NIAGARA5:
329 case SUN4V_CHIP_SPARC_M6:
330 case SUN4V_CHIP_SPARC_M7:
331 case SUN4V_CHIP_SPARC_M8:
332 case SUN4V_CHIP_SPARC_SN:
333 case SUN4V_CHIP_SPARC64X:
334 rover_inc_table = niagara_iterate_method;
335 break;
336 default:
337 rover_inc_table = generic_iterate_method;
338 }
339
340 for (level = t->nodes[root_index].level; level < CPUINFO_LVL_MAX;
341 level++) {
342 new_index = t->nodes[index].rover;
343 if (rover_inc_table[level] & ROVER_INC_ON_VISIT)
344 increment_rover(t, node_index: index, root_index, rover_inc_table);
345
346 index = new_index;
347 }
348 return index;
349}
350
351static void _cpu_map_rebuild(void)
352{
353 int i;
354
355 if (cpuinfo_tree) {
356 kfree(objp: cpuinfo_tree);
357 cpuinfo_tree = NULL;
358 }
359
360 cpuinfo_tree = build_cpuinfo_tree();
361 if (!cpuinfo_tree)
362 return;
363
364 /* Build CPU distribution map that spans all online CPUs. No need
365 * to check if the CPU is online, as that is done when the cpuinfo
366 * tree is being built.
367 */
368 for (i = 0; i < cpuinfo_tree->nodes[0].num_cpus; i++)
369 cpu_distribution_map[i] = iterate_cpu(t: cpuinfo_tree, root_index: 0);
370}
371
372/* Fallback if the cpuinfo tree could not be built. CPU mapping is linear
373 * round robin.
374 */
375static int simple_map_to_cpu(unsigned int index)
376{
377 int i, end, cpu_rover;
378
379 cpu_rover = 0;
380 end = index % num_online_cpus();
381 for (i = 0; i < num_possible_cpus(); i++) {
382 if (cpu_online(cpu: cpu_rover)) {
383 if (cpu_rover >= end)
384 return cpu_rover;
385
386 cpu_rover++;
387 }
388 }
389
390 /* Impossible, since num_online_cpus() <= num_possible_cpus() */
391 return cpumask_first(cpu_online_mask);
392}
393
394static int _map_to_cpu(unsigned int index)
395{
396 struct cpuinfo_node *root_node;
397
398 if (unlikely(!cpuinfo_tree)) {
399 _cpu_map_rebuild();
400 if (!cpuinfo_tree)
401 return simple_map_to_cpu(index);
402 }
403
404 root_node = &cpuinfo_tree->nodes[0];
405#ifdef CONFIG_HOTPLUG_CPU
406 if (unlikely(root_node->num_cpus != num_online_cpus())) {
407 _cpu_map_rebuild();
408 if (!cpuinfo_tree)
409 return simple_map_to_cpu(index);
410 }
411#endif
412 return cpu_distribution_map[index % root_node->num_cpus];
413}
414
415int map_to_cpu(unsigned int index)
416{
417 int mapped_cpu;
418 unsigned long flag;
419
420 spin_lock_irqsave(&cpu_map_lock, flag);
421 mapped_cpu = _map_to_cpu(index);
422
423#ifdef CONFIG_HOTPLUG_CPU
424 while (unlikely(!cpu_online(mapped_cpu)))
425 mapped_cpu = _map_to_cpu(index);
426#endif
427 spin_unlock_irqrestore(lock: &cpu_map_lock, flags: flag);
428 return mapped_cpu;
429}
430EXPORT_SYMBOL(map_to_cpu);
431
432void cpu_map_rebuild(void)
433{
434 unsigned long flag;
435
436 spin_lock_irqsave(&cpu_map_lock, flag);
437 _cpu_map_rebuild();
438 spin_unlock_irqrestore(lock: &cpu_map_lock, flags: flag);
439}
440

source code of linux/arch/sparc/kernel/cpumap.c