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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2016 Thomas Gleixner.
4 * Copyright (C) 2016-2017 Christoph Hellwig.
5 */
6#include <linux/kernel.h>
7#include <linux/slab.h>
8#include <linux/cpu.h>
9#include <linux/sort.h>
10#include <linux/group_cpus.h>
11
12#ifdef CONFIG_SMP
13
14static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
15 unsigned int cpus_per_grp)
16{
17 const struct cpumask *siblmsk;
18 int cpu, sibl;
19
20 for ( ; cpus_per_grp > 0; ) {
21 cpu = cpumask_first(nmsk);
22
23 /* Should not happen, but I'm too lazy to think about it */
24 if (cpu >= nr_cpu_ids)
25 return;
26
27 cpumask_clear_cpu(cpu, nmsk);
28 cpumask_set_cpu(cpu, irqmsk);
29 cpus_per_grp--;
30
31 /* If the cpu has siblings, use them first */
32 siblmsk = topology_sibling_cpumask(cpu);
33 for (sibl = -1; cpus_per_grp > 0; ) {
34 sibl = cpumask_next(sibl, siblmsk);
35 if (sibl >= nr_cpu_ids)
36 break;
37 if (!cpumask_test_and_clear_cpu(sibl, nmsk))
38 continue;
39 cpumask_set_cpu(sibl, irqmsk);
40 cpus_per_grp--;
41 }
42 }
43}
44
45static cpumask_var_t *alloc_node_to_cpumask(void)
46{
47 cpumask_var_t *masks;
48 int node;
49
50 masks = kzalloc_objs(cpumask_var_t, nr_node_ids);
51 if (!masks)
52 return NULL;
53
54 for (node = 0; node < nr_node_ids; node++) {
55 if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
56 goto out_unwind;
57 }
58
59 return masks;
60
61out_unwind:
62 while (--node >= 0)
63 free_cpumask_var(masks[node]);
64 kfree(masks);
65 return NULL;
66}
67
68static void free_node_to_cpumask(cpumask_var_t *masks)
69{
70 int node;
71
72 for (node = 0; node < nr_node_ids; node++)
73 free_cpumask_var(masks[node]);
74 kfree(masks);
75}
76
77static void build_node_to_cpumask(cpumask_var_t *masks)
78{
79 int cpu;
80
81 for_each_possible_cpu(cpu)
82 cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
83}
84
85static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
86 const struct cpumask *mask, nodemask_t *nodemsk)
87{
88 int n, nodes = 0;
89
90 /* Calculate the number of nodes in the supplied affinity mask */
91 for_each_node(n) {
92 if (cpumask_intersects(mask, node_to_cpumask[n])) {
93 node_set(n, *nodemsk);
94 nodes++;
95 }
96 }
97 return nodes;
98}
99
100struct node_groups {
101 unsigned id;
102
103 union {
104 unsigned ngroups;
105 unsigned ncpus;
106 };
107};
108
109static int ncpus_cmp_func(const void *l, const void *r)
110{
111 const struct node_groups *ln = l;
112 const struct node_groups *rn = r;
113
114 return ln->ncpus - rn->ncpus;
115}
116
117static void alloc_groups_to_nodes(unsigned int numgrps,
118 unsigned int numcpus,
119 struct node_groups *node_groups,
120 unsigned int num_nodes)
121{
122 unsigned int n, remaining_ncpus = numcpus;
123 unsigned int ngroups, ncpus;
124
125 sort(node_groups, num_nodes, sizeof(node_groups[0]),
126 ncpus_cmp_func, NULL);
127
128 /*
129 * Allocate groups for each node according to the ratio of this
130 * node's nr_cpus to remaining un-assigned ncpus. 'numgrps' is
131 * bigger than number of active numa nodes. Always start the
132 * allocation from the node with minimized nr_cpus.
133 *
134 * This way guarantees that each active node gets allocated at
135 * least one group, and the theory is simple: over-allocation
136 * is only done when this node is assigned by one group, so
137 * other nodes will be allocated >= 1 groups, since 'numgrps' is
138 * bigger than number of numa nodes.
139 *
140 * One perfect invariant is that number of allocated groups for
141 * each node is <= CPU count of this node:
142 *
143 * 1) suppose there are two nodes: A and B
144 * ncpu(X) is CPU count of node X
145 * grps(X) is the group count allocated to node X via this
146 * algorithm
147 *
148 * ncpu(A) <= ncpu(B)
149 * ncpu(A) + ncpu(B) = N
150 * grps(A) + grps(B) = G
151 *
152 * grps(A) = max(1, round_down(G * ncpu(A) / N))
153 * grps(B) = G - grps(A)
154 *
155 * both N and G are integer, and 2 <= G <= N, suppose
156 * G = N - delta, and 0 <= delta <= N - 2
157 *
158 * 2) obviously grps(A) <= ncpu(A) because:
159 *
160 * if grps(A) is 1, then grps(A) <= ncpu(A) given
161 * ncpu(A) >= 1
162 *
163 * otherwise,
164 * grps(A) <= G * ncpu(A) / N <= ncpu(A), given G <= N
165 *
166 * 3) prove how grps(B) <= ncpu(B):
167 *
168 * if round_down(G * ncpu(A) / N) == 0, vecs(B) won't be
169 * over-allocated, so grps(B) <= ncpu(B),
170 *
171 * otherwise:
172 *
173 * grps(A) =
174 * round_down(G * ncpu(A) / N) =
175 * round_down((N - delta) * ncpu(A) / N) =
176 * round_down((N * ncpu(A) - delta * ncpu(A)) / N) >=
177 * round_down((N * ncpu(A) - delta * N) / N) =
178 * cpu(A) - delta
179 *
180 * then:
181 *
182 * grps(A) - G >= ncpu(A) - delta - G
183 * =>
184 * G - grps(A) <= G + delta - ncpu(A)
185 * =>
186 * grps(B) <= N - ncpu(A)
187 * =>
188 * grps(B) <= cpu(B)
189 *
190 * For nodes >= 3, it can be thought as one node and another big
191 * node given that is exactly what this algorithm is implemented,
192 * and we always re-calculate 'remaining_ncpus' & 'numgrps', and
193 * finally for each node X: grps(X) <= ncpu(X).
194 *
195 */
196
197 for (n = 0; n < num_nodes; n++) {
198 if (node_groups[n].ncpus == UINT_MAX)
199 continue;
200
201 WARN_ON_ONCE(numgrps == 0);
202
203 ncpus = node_groups[n].ncpus;
204 ngroups = max_t(unsigned, 1,
205 numgrps * ncpus / remaining_ncpus);
206 WARN_ON_ONCE(ngroups > ncpus);
207
208 node_groups[n].ngroups = ngroups;
209
210 remaining_ncpus -= ncpus;
211 numgrps -= ngroups;
212 }
213}
214
215/*
216 * Allocate group number for each node, so that for each node:
217 *
218 * 1) the allocated number is >= 1
219 *
220 * 2) the allocated number is <= active CPU number of this node
221 *
222 * The actual allocated total groups may be less than @numgrps when
223 * active total CPU number is less than @numgrps.
224 *
225 * Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
226 * for each node.
227 */
228static void alloc_nodes_groups(unsigned int numgrps,
229 cpumask_var_t *node_to_cpumask,
230 const struct cpumask *cpu_mask,
231 const nodemask_t nodemsk,
232 struct cpumask *nmsk,
233 struct node_groups *node_groups)
234{
235 unsigned int n, numcpus = 0;
236
237 for (n = 0; n < nr_node_ids; n++) {
238 node_groups[n].id = n;
239 node_groups[n].ncpus = UINT_MAX;
240 }
241
242 for_each_node_mask(n, nodemsk) {
243 unsigned int ncpus;
244
245 cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
246 ncpus = cpumask_weight(nmsk);
247
248 if (!ncpus)
249 continue;
250 numcpus += ncpus;
251 node_groups[n].ncpus = ncpus;
252 }
253
254 numgrps = min_t(unsigned int, numcpus, numgrps);
255 alloc_groups_to_nodes(numgrps, numcpus, node_groups, nr_node_ids);
256}
257
258static void assign_cpus_to_groups(unsigned int ncpus,
259 struct cpumask *nmsk,
260 struct node_groups *nv,
261 struct cpumask *masks,
262 unsigned int *curgrp,
263 unsigned int last_grp)
264{
265 unsigned int v, cpus_per_grp, extra_grps;
266 /* Account for rounding errors */
267 extra_grps = ncpus - nv->ngroups * (ncpus / nv->ngroups);
268
269 /* Spread allocated groups on CPUs of the current node */
270 for (v = 0; v < nv->ngroups; v++, *curgrp += 1) {
271 cpus_per_grp = ncpus / nv->ngroups;
272
273 /* Account for extra groups to compensate rounding errors */
274 if (extra_grps) {
275 cpus_per_grp++;
276 --extra_grps;
277 }
278
279 /*
280 * wrapping has to be considered given 'startgrp'
281 * may start anywhere
282 */
283 if (*curgrp >= last_grp)
284 *curgrp = 0;
285 grp_spread_init_one(&masks[*curgrp], nmsk, cpus_per_grp);
286 }
287}
288
289static int alloc_cluster_groups(unsigned int ncpus,
290 unsigned int ngroups,
291 struct cpumask *node_cpumask,
292 cpumask_var_t msk,
293 const struct cpumask ***clusters_ptr,
294 struct node_groups **cluster_groups_ptr)
295{
296 unsigned int ncluster = 0;
297 unsigned int cpu, nc, n;
298 const struct cpumask *cluster_mask;
299 const struct cpumask **clusters;
300 struct node_groups *cluster_groups;
301
302 cpumask_copy(msk, node_cpumask);
303
304 /* Probe how many clusters in this node. */
305 while (1) {
306 cpu = cpumask_first(msk);
307 if (cpu >= nr_cpu_ids)
308 break;
309
310 cluster_mask = topology_cluster_cpumask(cpu);
311 if (!cpumask_weight(cluster_mask))
312 goto no_cluster;
313 /* Clean out CPUs on the same cluster. */
314 cpumask_andnot(msk, msk, cluster_mask);
315 ncluster++;
316 }
317
318 /* If ngroups < ncluster, cross cluster is inevitable, skip. */
319 if (ncluster == 0 || ncluster > ngroups)
320 goto no_cluster;
321
322 /* Allocate memory based on cluster number. */
323 clusters = kzalloc_objs(*clusters, ncluster);
324 if (!clusters)
325 goto no_cluster;
326 cluster_groups = kzalloc_objs(struct node_groups, ncluster);
327 if (!cluster_groups)
328 goto fail_cluster_groups;
329
330 /* Filling cluster info for later process. */
331 cpumask_copy(msk, node_cpumask);
332 for (n = 0; n < ncluster; n++) {
333 cpu = cpumask_first(msk);
334 cluster_mask = topology_cluster_cpumask(cpu);
335 nc = cpumask_weight_and(cluster_mask, node_cpumask);
336 clusters[n] = cluster_mask;
337 cluster_groups[n].id = n;
338 cluster_groups[n].ncpus = nc;
339 cpumask_andnot(msk, msk, cluster_mask);
340 }
341
342 alloc_groups_to_nodes(ngroups, ncpus, cluster_groups, ncluster);
343
344 *clusters_ptr = clusters;
345 *cluster_groups_ptr = cluster_groups;
346 return ncluster;
347
348 fail_cluster_groups:
349 kfree(clusters);
350 no_cluster:
351 return 0;
352}
353
354/*
355 * Try group CPUs evenly for cluster locality within a NUMA node.
356 *
357 * Return: true if success, false otherwise.
358 */
359static bool __try_group_cluster_cpus(unsigned int ncpus,
360 unsigned int ngroups,
361 struct cpumask *node_cpumask,
362 struct cpumask *masks,
363 unsigned int *curgrp,
364 unsigned int last_grp)
365{
366 struct node_groups *cluster_groups;
367 const struct cpumask **clusters;
368 unsigned int ncluster;
369 bool ret = false;
370 cpumask_var_t nmsk;
371 unsigned int i, nc;
372
373 if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
374 goto fail_nmsk_alloc;
375
376 ncluster = alloc_cluster_groups(ncpus, ngroups, node_cpumask, nmsk,
377 &clusters, &cluster_groups);
378
379 if (ncluster == 0)
380 goto fail_no_clusters;
381
382 for (i = 0; i < ncluster; i++) {
383 struct node_groups *nv = &cluster_groups[i];
384
385 /* Get the cpus on this cluster. */
386 cpumask_and(nmsk, node_cpumask, clusters[nv->id]);
387 nc = cpumask_weight(nmsk);
388 if (!nc)
389 continue;
390 WARN_ON_ONCE(nv->ngroups > nc);
391
392 assign_cpus_to_groups(nc, nmsk, nv, masks, curgrp, last_grp);
393 }
394
395 ret = true;
396 kfree(cluster_groups);
397 kfree(clusters);
398 fail_no_clusters:
399 free_cpumask_var(nmsk);
400 fail_nmsk_alloc:
401 return ret;
402}
403
404static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
405 cpumask_var_t *node_to_cpumask,
406 const struct cpumask *cpu_mask,
407 struct cpumask *nmsk, struct cpumask *masks)
408{
409 unsigned int i, n, nodes, done = 0;
410 unsigned int last_grp = numgrps;
411 unsigned int curgrp = startgrp;
412 nodemask_t nodemsk = NODE_MASK_NONE;
413 struct node_groups *node_groups;
414
415 if (cpumask_empty(cpu_mask))
416 return 0;
417
418 nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);
419
420 /*
421 * If the number of nodes in the mask is greater than or equal the
422 * number of groups we just spread the groups across the nodes.
423 */
424 if (numgrps <= nodes) {
425 for_each_node_mask(n, nodemsk) {
426 /* Ensure that only CPUs which are in both masks are set */
427 cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
428 cpumask_or(&masks[curgrp], &masks[curgrp], nmsk);
429 if (++curgrp == last_grp)
430 curgrp = 0;
431 }
432 return numgrps;
433 }
434
435 node_groups = kzalloc_objs(struct node_groups, nr_node_ids);
436 if (!node_groups)
437 return -ENOMEM;
438
439 /* allocate group number for each node */
440 alloc_nodes_groups(numgrps, node_to_cpumask, cpu_mask,
441 nodemsk, nmsk, node_groups);
442 for (i = 0; i < nr_node_ids; i++) {
443 unsigned int ncpus;
444 struct node_groups *nv = &node_groups[i];
445
446 if (nv->ngroups == UINT_MAX)
447 continue;
448
449 /* Get the cpus on this node which are in the mask */
450 cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]);
451 ncpus = cpumask_weight(nmsk);
452 if (!ncpus)
453 continue;
454
455 WARN_ON_ONCE(nv->ngroups > ncpus);
456
457 if (__try_group_cluster_cpus(ncpus, nv->ngroups, nmsk,
458 masks, &curgrp, last_grp)) {
459 done += nv->ngroups;
460 continue;
461 }
462
463 assign_cpus_to_groups(ncpus, nmsk, nv, masks, &curgrp,
464 last_grp);
465 done += nv->ngroups;
466 }
467 kfree(node_groups);
468 return done;
469}
470
471/**
472 * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
473 * @numgrps: number of groups
474 * @nummasks: number of initialized cpumasks
475 *
476 * Return: cpumask array if successful, NULL otherwise. And each element
477 * includes CPUs assigned to this group. nummasks contains the number
478 * of initialized masks which can be less than numgrps.
479 *
480 * Try to put close CPUs from viewpoint of CPU and NUMA locality into
481 * same group, and run two-stage grouping:
482 * 1) allocate present CPUs on these groups evenly first
483 * 2) allocate other possible CPUs on these groups evenly
484 *
485 * We guarantee in the resulted grouping that all CPUs are covered, and
486 * no same CPU is assigned to multiple groups
487 */
488struct cpumask *group_cpus_evenly(unsigned int numgrps, unsigned int *nummasks)
489{
490 unsigned int curgrp = 0, nr_present = 0, nr_others = 0;
491 cpumask_var_t *node_to_cpumask;
492 cpumask_var_t nmsk, npresmsk;
493 int ret = -ENOMEM;
494 struct cpumask *masks = NULL;
495
496 if (numgrps == 0)
497 return NULL;
498
499 if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
500 return NULL;
501
502 if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL))
503 goto fail_nmsk;
504
505 node_to_cpumask = alloc_node_to_cpumask();
506 if (!node_to_cpumask)
507 goto fail_npresmsk;
508
509 masks = kzalloc_objs(*masks, numgrps);
510 if (!masks)
511 goto fail_node_to_cpumask;
512
513 build_node_to_cpumask(node_to_cpumask);
514
515 /*
516 * Make a local cache of 'cpu_present_mask', so the two stages
517 * spread can observe consistent 'cpu_present_mask' without holding
518 * cpu hotplug lock, then we can reduce deadlock risk with cpu
519 * hotplug code.
520 *
521 * Here CPU hotplug may happen when reading `cpu_present_mask`, and
522 * we can live with the case because it only affects that hotplug
523 * CPU is handled in the 1st or 2nd stage, and either way is correct
524 * from API user viewpoint since 2-stage spread is sort of
525 * optimization.
526 */
527 cpumask_copy(npresmsk, data_race(cpu_present_mask));
528
529 /* grouping present CPUs first */
530 ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
531 npresmsk, nmsk, masks);
532 if (ret < 0)
533 goto fail_node_to_cpumask;
534 nr_present = ret;
535
536 /*
537 * Allocate non present CPUs starting from the next group to be
538 * handled. If the grouping of present CPUs already exhausted the
539 * group space, assign the non present CPUs to the already
540 * allocated out groups.
541 */
542 if (nr_present >= numgrps)
543 curgrp = 0;
544 else
545 curgrp = nr_present;
546 cpumask_andnot(npresmsk, cpu_possible_mask, npresmsk);
547 ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
548 npresmsk, nmsk, masks);
549 if (ret >= 0)
550 nr_others = ret;
551
552 fail_node_to_cpumask:
553 free_node_to_cpumask(node_to_cpumask);
554
555 fail_npresmsk:
556 free_cpumask_var(npresmsk);
557
558 fail_nmsk:
559 free_cpumask_var(nmsk);
560 if (ret < 0) {
561 kfree(masks);
562 return NULL;
563 }
564 *nummasks = min(nr_present + nr_others, numgrps);
565 return masks;
566}
567#else /* CONFIG_SMP */
568struct cpumask *group_cpus_evenly(unsigned int numgrps, unsigned int *nummasks)
569{
570 struct cpumask *masks;
571
572 if (numgrps == 0)
573 return NULL;
574
575 masks = kzalloc_objs(*masks, numgrps);
576 if (!masks)
577 return NULL;
578
579 /* assign all CPUs(cpu 0) to the 1st group only */
580 cpumask_copy(&masks[0], cpu_possible_mask);
581 *nummasks = 1;
582 return masks;
583}
584#endif /* CONFIG_SMP */
585EXPORT_SYMBOL_GPL(group_cpus_evenly);