kernel/irq/affinity.c

   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/interrupt.h>
   7 #include <linux/kernel.h>
   8 #include <linux/slab.h>
   9 #include <linux/cpu.h>
  10 #include <linux/sort.h>
  11
  12 static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
  13                                 unsigned int cpus_per_vec)
  14 {
  15         const struct cpumask *siblmsk;
  16         int cpu, sibl;
  17
  18         for ( ; cpus_per_vec > 0; ) {
  19                 cpu = cpumask_first(nmsk);
  20
  21                 /* Should not happen, but I'm too lazy to think about it */
  22                 if (cpu >= nr_cpu_ids)
  23                         return;
  24
  25                 cpumask_clear_cpu(cpu, nmsk);
  26                 cpumask_set_cpu(cpu, irqmsk);
  27                 cpus_per_vec--;
  28
  29                 /* If the cpu has siblings, use them first */
  30                 siblmsk = topology_sibling_cpumask(cpu);
  31                 for (sibl = -1; cpus_per_vec > 0; ) {
  32                         sibl = cpumask_next(sibl, siblmsk);
  33                         if (sibl >= nr_cpu_ids)
  34                                 break;
  35                         if (!cpumask_test_and_clear_cpu(sibl, nmsk))
  36                                 continue;
  37                         cpumask_set_cpu(sibl, irqmsk);
  38                         cpus_per_vec--;
  39                 }
  40         }
  41 }
  42
  43 static cpumask_var_t *alloc_node_to_cpumask(void)
  44 {
  45         cpumask_var_t *masks;
  46         int node;
  47
  48         masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
  49         if (!masks)
  50                 return NULL;
  51
  52         for (node = 0; node < nr_node_ids; node++) {
  53                 if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
  54                         goto out_unwind;
  55         }
  56
  57         return masks;
  58
  59 out_unwind:
  60         while (--node >= 0)
  61                 free_cpumask_var(masks[node]);
  62         kfree(masks);
  63         return NULL;
  64 }
  65
  66 static void free_node_to_cpumask(cpumask_var_t *masks)
  67 {
  68         int node;
  69
  70         for (node = 0; node < nr_node_ids; node++)
  71                 free_cpumask_var(masks[node]);
  72         kfree(masks);
  73 }
  74
  75 static void build_node_to_cpumask(cpumask_var_t *masks)
  76 {
  77         int cpu;
  78
  79         for_each_possible_cpu(cpu)
  80                 cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
  81 }
  82
  83 static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
  84                                 const struct cpumask *mask, nodemask_t *nodemsk)
  85 {
  86         int n, nodes = 0;
  87
  88         /* Calculate the number of nodes in the supplied affinity mask */
  89         for_each_node(n) {
  90                 if (cpumask_intersects(mask, node_to_cpumask[n])) {
  91                         node_set(n, *nodemsk);
  92                         nodes++;
  93                 }
  94         }
  95         return nodes;
  96 }
  97
  98 struct node_vectors {
  99         unsigned id;
 100
 101         union {
 102                 unsigned nvectors;
 103                 unsigned ncpus;
 104         };
 105 };
 106
 107 static int ncpus_cmp_func(const void *l, const void *r)
 108 {
 109         const struct node_vectors *ln = l;
 110         const struct node_vectors *rn = r;
 111
 112         return ln->ncpus - rn->ncpus;
 113 }
 114
 115 /*
 116  * Allocate vector number for each node, so that for each node:
 117  *
 118  * 1) the allocated number is >= 1
 119  *
 120  * 2) the allocated numbver is <= active CPU number of this node
 121  *
 122  * The actual allocated total vectors may be less than @numvecs when
 123  * active total CPU number is less than @numvecs.
 124  *
 125  * Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
 126  * for each node.
 127  */
 128 static void alloc_nodes_vectors(unsigned int numvecs,
 129                                 cpumask_var_t *node_to_cpumask,
 130                                 const struct cpumask *cpu_mask,
 131                                 const nodemask_t nodemsk,
 132                                 struct cpumask *nmsk,
 133                                 struct node_vectors *node_vectors)
 134 {
 135         unsigned n, remaining_ncpus = 0;
 136
 137         for (n = 0; n < nr_node_ids; n++) {
 138                 node_vectors[n].id = n;
 139                 node_vectors[n].ncpus = UINT_MAX;
 140         }
 141
 142         for_each_node_mask(n, nodemsk) {
 143                 unsigned ncpus;
 144
 145                 cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
 146                 ncpus = cpumask_weight(nmsk);
 147
 148                 if (!ncpus)
 149                         continue;
 150                 remaining_ncpus += ncpus;
 151                 node_vectors[n].ncpus = ncpus;
 152         }
 153
 154         numvecs = min_t(unsigned, remaining_ncpus, numvecs);
 155
 156         sort(node_vectors, nr_node_ids, sizeof(node_vectors[0]),
 157              ncpus_cmp_func, NULL);
 158
 159         /*
 160          * Allocate vectors for each node according to the ratio of this
 161          * node's nr_cpus to remaining un-assigned ncpus. 'numvecs' is
 162          * bigger than number of active numa nodes. Always start the
 163          * allocation from the node with minimized nr_cpus.
 164          *
 165          * This way guarantees that each active node gets allocated at
 166          * least one vector, and the theory is simple: over-allocation
 167          * is only done when this node is assigned by one vector, so
 168          * other nodes will be allocated >= 1 vector, since 'numvecs' is
 169          * bigger than number of numa nodes.
 170          *
 171          * One perfect invariant is that number of allocated vectors for
 172          * each node is <= CPU count of this node:
 173          *
 174          * 1) suppose there are two nodes: A and B
 175          *      ncpu(X) is CPU count of node X
 176          *      vecs(X) is the vector count allocated to node X via this
 177          *      algorithm
 178          *
 179          *      ncpu(A) <= ncpu(B)
 180          *      ncpu(A) + ncpu(B) = N
 181          *      vecs(A) + vecs(B) = V
 182          *
 183          *      vecs(A) = max(1, round_down(V * ncpu(A) / N))
 184          *      vecs(B) = V - vecs(A)
 185          *
 186          *      both N and V are integer, and 2 <= V <= N, suppose
 187          *      V = N - delta, and 0 <= delta <= N - 2
 188          *
 189          * 2) obviously vecs(A) <= ncpu(A) because:
 190          *
 191          *      if vecs(A) is 1, then vecs(A) <= ncpu(A) given
 192          *      ncpu(A) >= 1
 193          *
 194          *      otherwise,
 195          *              vecs(A) <= V * ncpu(A) / N <= ncpu(A), given V <= N
 196          *
 197          * 3) prove how vecs(B) <= ncpu(B):
 198          *
 199          *      if round_down(V * ncpu(A) / N) == 0, vecs(B) won't be
 200          *      over-allocated, so vecs(B) <= ncpu(B),
 201          *
 202          *      otherwise:
 203          *
 204          *      vecs(A) =
 205          *              round_down(V * ncpu(A) / N) =
 206          *              round_down((N - delta) * ncpu(A) / N) =
 207          *              round_down((N * ncpu(A) - delta * ncpu(A)) / N)  >=
 208          *              round_down((N * ncpu(A) - delta * N) / N)        =
 209          *              cpu(A) - delta
 210          *
 211          *      then:
 212          *
 213          *      vecs(A) - V >= ncpu(A) - delta - V
 214          *      =>
 215          *      V - vecs(A) <= V + delta - ncpu(A)
 216          *      =>
 217          *      vecs(B) <= N - ncpu(A)
 218          *      =>
 219          *      vecs(B) <= cpu(B)
 220          *
 221          * For nodes >= 3, it can be thought as one node and another big
 222          * node given that is exactly what this algorithm is implemented,
 223          * and we always re-calculate 'remaining_ncpus' & 'numvecs', and
 224          * finally for each node X: vecs(X) <= ncpu(X).
 225          *
 226          */
 227         for (n = 0; n < nr_node_ids; n++) {
 228                 unsigned nvectors, ncpus;
 229
 230                 if (node_vectors[n].ncpus == UINT_MAX)
 231                         continue;
 232
 233                 WARN_ON_ONCE(numvecs == 0);
 234
 235                 ncpus = node_vectors[n].ncpus;
 236                 nvectors = max_t(unsigned, 1,
 237                                  numvecs * ncpus / remaining_ncpus);
 238                 WARN_ON_ONCE(nvectors > ncpus);
 239
 240                 node_vectors[n].nvectors = nvectors;
 241
 242                 remaining_ncpus -= ncpus;
 243                 numvecs -= nvectors;
 244         }
 245 }
 246
 247 static int __irq_build_affinity_masks(unsigned int startvec,
 248                                       unsigned int numvecs,
 249                                       unsigned int firstvec,
 250                                       cpumask_var_t *node_to_cpumask,
 251                                       const struct cpumask *cpu_mask,
 252                                       struct cpumask *nmsk,
 253                                       struct irq_affinity_desc *masks)
 254 {
 255         unsigned int i, n, nodes, cpus_per_vec, extra_vecs, done = 0;
 256         unsigned int last_affv = firstvec + numvecs;
 257         unsigned int curvec = startvec;
 258         nodemask_t nodemsk = NODE_MASK_NONE;
 259         struct node_vectors *node_vectors;
 260
 261         if (!cpumask_weight(cpu_mask))
 262                 return 0;
 263
 264         nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);
 265
 266         /*
 267          * If the number of nodes in the mask is greater than or equal the
 268          * number of vectors we just spread the vectors across the nodes.
 269          */
 270         if (numvecs <= nodes) {
 271                 for_each_node_mask(n, nodemsk) {
 272                         cpumask_or(&masks[curvec].mask, &masks[curvec].mask,
 273                                    node_to_cpumask[n]);
 274                         if (++curvec == last_affv)
 275                                 curvec = firstvec;
 276                 }
 277                 return numvecs;
 278         }
 279
 280         node_vectors = kcalloc(nr_node_ids,
 281                                sizeof(struct node_vectors),
 282                                GFP_KERNEL);
 283         if (!node_vectors)
 284                 return -ENOMEM;
 285
 286         /* allocate vector number for each node */
 287         alloc_nodes_vectors(numvecs, node_to_cpumask, cpu_mask,
 288                             nodemsk, nmsk, node_vectors);
 289
 290         for (i = 0; i < nr_node_ids; i++) {
 291                 unsigned int ncpus, v;
 292                 struct node_vectors *nv = &node_vectors[i];
 293
 294                 if (nv->nvectors == UINT_MAX)
 295                         continue;
 296
 297                 /* Get the cpus on this node which are in the mask */
 298                 cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]);
 299                 ncpus = cpumask_weight(nmsk);
 300                 if (!ncpus)
 301                         continue;
 302
 303                 WARN_ON_ONCE(nv->nvectors > ncpus);
 304
 305                 /* Account for rounding errors */
 306                 extra_vecs = ncpus - nv->nvectors * (ncpus / nv->nvectors);
 307
 308                 /* Spread allocated vectors on CPUs of the current node */
 309                 for (v = 0; v < nv->nvectors; v++, curvec++) {
 310                         cpus_per_vec = ncpus / nv->nvectors;
 311
 312                         /* Account for extra vectors to compensate rounding errors */
 313                         if (extra_vecs) {
 314                                 cpus_per_vec++;
 315                                 --extra_vecs;
 316                         }
 317
 318                         /*
 319                          * wrapping has to be considered given 'startvec'
 320                          * may start anywhere
 321                          */
 322                         if (curvec >= last_affv)
 323                                 curvec = firstvec;
 324                         irq_spread_init_one(&masks[curvec].mask, nmsk,
 325                                                 cpus_per_vec);
 326                 }
 327                 done += nv->nvectors;
 328         }
 329         kfree(node_vectors);
 330         return done;
 331 }
 332
 333 /*
 334  * build affinity in two stages:
 335  *      1) spread present CPU on these vectors
 336  *      2) spread other possible CPUs on these vectors
 337  */
 338 static int irq_build_affinity_masks(unsigned int startvec, unsigned int numvecs,
 339                                     unsigned int firstvec,
 340                                     struct irq_affinity_desc *masks)
 341 {
 342         unsigned int curvec = startvec, nr_present = 0, nr_others = 0;
 343         cpumask_var_t *node_to_cpumask;
 344         cpumask_var_t nmsk, npresmsk;
 345         int ret = -ENOMEM;
 346
 347         if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 348                 return ret;
 349
 350         if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL))
 351                 goto fail_nmsk;
 352
 353         node_to_cpumask = alloc_node_to_cpumask();
 354         if (!node_to_cpumask)
 355                 goto fail_npresmsk;
 356
 357         /* Stabilize the cpumasks */
 358         get_online_cpus();
 359         build_node_to_cpumask(node_to_cpumask);
 360
 361         /* Spread on present CPUs starting from affd->pre_vectors */
 362         ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
 363                                          node_to_cpumask, cpu_present_mask,
 364                                          nmsk, masks);
 365         if (ret < 0)
 366                 goto fail_build_affinity;
 367         nr_present = ret;
 368
 369         /*
 370          * Spread on non present CPUs starting from the next vector to be
 371          * handled. If the spreading of present CPUs already exhausted the
 372          * vector space, assign the non present CPUs to the already spread
 373          * out vectors.
 374          */
 375         if (nr_present >= numvecs)
 376                 curvec = firstvec;
 377         else
 378                 curvec = firstvec + nr_present;
 379         cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
 380         ret = __irq_build_affinity_masks(curvec, numvecs, firstvec,
 381                                          node_to_cpumask, npresmsk, nmsk,
 382                                          masks);
 383         if (ret >= 0)
 384                 nr_others = ret;
 385
 386  fail_build_affinity:
 387         put_online_cpus();
 388
 389         if (ret >= 0)
 390                 WARN_ON(nr_present + nr_others < numvecs);
 391
 392         free_node_to_cpumask(node_to_cpumask);
 393
 394  fail_npresmsk:
 395         free_cpumask_var(npresmsk);
 396
 397  fail_nmsk:
 398         free_cpumask_var(nmsk);
 399         return ret < 0 ? ret : 0;
 400 }
 401
 402 static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
 403 {
 404         affd->nr_sets = 1;
 405         affd->set_size[0] = affvecs;
 406 }
 407
 408 /**
 409  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
 410  * @nvecs:      The total number of vectors
 411  * @affd:       Description of the affinity requirements
 412  *
 413  * Returns the irq_affinity_desc pointer or NULL if allocation failed.
 414  */
 415 struct irq_affinity_desc *
 416 irq_create_affinity_masks(unsigned int nvecs, struct irq_affinity *affd)
 417 {
 418         unsigned int affvecs, curvec, usedvecs, i;
 419         struct irq_affinity_desc *masks = NULL;
 420
 421         /*
 422          * Determine the number of vectors which need interrupt affinities
 423          * assigned. If the pre/post request exhausts the available vectors
 424          * then nothing to do here except for invoking the calc_sets()
 425          * callback so the device driver can adjust to the situation.
 426          */
 427         if (nvecs > affd->pre_vectors + affd->post_vectors)
 428                 affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
 429         else
 430                 affvecs = 0;
 431
 432         /*
 433          * Simple invocations do not provide a calc_sets() callback. Install
 434          * the generic one.
 435          */
 436         if (!affd->calc_sets)
 437                 affd->calc_sets = default_calc_sets;
 438
 439         /* Recalculate the sets */
 440         affd->calc_sets(affd, affvecs);
 441
 442         if (WARN_ON_ONCE(affd->nr_sets > IRQ_AFFINITY_MAX_SETS))
 443                 return NULL;
 444
 445         /* Nothing to assign? */
 446         if (!affvecs)
 447                 return NULL;
 448
 449         masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
 450         if (!masks)
 451                 return NULL;
 452
 453         /* Fill out vectors at the beginning that don't need affinity */
 454         for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 455                 cpumask_copy(&masks[curvec].mask, irq_default_affinity);
 456
 457         /*
 458          * Spread on present CPUs starting from affd->pre_vectors. If we
 459          * have multiple sets, build each sets affinity mask separately.
 460          */
 461         for (i = 0, usedvecs = 0; i < affd->nr_sets; i++) {
 462                 unsigned int this_vecs = affd->set_size[i];
 463                 int ret;
 464
 465                 ret = irq_build_affinity_masks(curvec, this_vecs,
 466                                                curvec, masks);
 467                 if (ret) {
 468                         kfree(masks);
 469                         return NULL;
 470                 }
 471                 curvec += this_vecs;
 472                 usedvecs += this_vecs;
 473         }
 474
 475         /* Fill out vectors at the end that don't need affinity */
 476         if (usedvecs >= affvecs)
 477                 curvec = affd->pre_vectors + affvecs;
 478         else
 479                 curvec = affd->pre_vectors + usedvecs;
 480         for (; curvec < nvecs; curvec++)
 481                 cpumask_copy(&masks[curvec].mask, irq_default_affinity);
 482
 483         /* Mark the managed interrupts */
 484         for (i = affd->pre_vectors; i < nvecs - affd->post_vectors; i++)
 485                 masks[i].is_managed = 1;
 486
 487         return masks;
 488 }
 489
 490 /**
 491  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
 492  * @minvec:     The minimum number of vectors available
 493  * @maxvec:     The maximum number of vectors available
 494  * @affd:       Description of the affinity requirements
 495  */
 496 unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
 497                                        const struct irq_affinity *affd)
 498 {
 499         unsigned int resv = affd->pre_vectors + affd->post_vectors;
 500         unsigned int set_vecs;
 501
 502         if (resv > minvec)
 503                 return 0;
 504
 505         if (affd->calc_sets) {
 506                 set_vecs = maxvec - resv;
 507         } else {
 508                 get_online_cpus();
 509                 set_vecs = cpumask_weight(cpu_possible_mask);
 510                 put_online_cpus();
 511         }
 512
 513         return resv + min(set_vecs, maxvec - resv);
 514 }