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
  11 static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
  12                                 int cpus_per_vec)
  13 {
  14         const struct cpumask *siblmsk;
  15         int cpu, sibl;
  16
  17         for ( ; cpus_per_vec > 0; ) {
  18                 cpu = cpumask_first(nmsk);
  19
  20                 /* Should not happen, but I'm too lazy to think about it */
  21                 if (cpu >= nr_cpu_ids)
  22                         return;
  23
  24                 cpumask_clear_cpu(cpu, nmsk);
  25                 cpumask_set_cpu(cpu, irqmsk);
  26                 cpus_per_vec--;
  27
  28                 /* If the cpu has siblings, use them first */
  29                 siblmsk = topology_sibling_cpumask(cpu);
  30                 for (sibl = -1; cpus_per_vec > 0; ) {
  31                         sibl = cpumask_next(sibl, siblmsk);
  32                         if (sibl >= nr_cpu_ids)
  33                                 break;
  34                         if (!cpumask_test_and_clear_cpu(sibl, nmsk))
  35                                 continue;
  36                         cpumask_set_cpu(sibl, irqmsk);
  37                         cpus_per_vec--;
  38                 }
  39         }
  40 }
  41
  42 static cpumask_var_t *alloc_node_to_present_cpumask(void)
  43 {
  44         cpumask_var_t *masks;
  45         int node;
  46
  47         masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
  48         if (!masks)
  49                 return NULL;
  50
  51         for (node = 0; node < nr_node_ids; node++) {
  52                 if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
  53                         goto out_unwind;
  54         }
  55
  56         return masks;
  57
  58 out_unwind:
  59         while (--node >= 0)
  60                 free_cpumask_var(masks[node]);
  61         kfree(masks);
  62         return NULL;
  63 }
  64
  65 static void free_node_to_present_cpumask(cpumask_var_t *masks)
  66 {
  67         int node;
  68
  69         for (node = 0; node < nr_node_ids; node++)
  70                 free_cpumask_var(masks[node]);
  71         kfree(masks);
  72 }
  73
  74 static void build_node_to_present_cpumask(cpumask_var_t *masks)
  75 {
  76         int cpu;
  77
  78         for_each_present_cpu(cpu)
  79                 cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
  80 }
  81
  82 static int get_nodes_in_cpumask(cpumask_var_t *node_to_present_cpumask,
  83                                 const struct cpumask *mask, nodemask_t *nodemsk)
  84 {
  85         int n, nodes = 0;
  86
  87         /* Calculate the number of nodes in the supplied affinity mask */
  88         for_each_node(n) {
  89                 if (cpumask_intersects(mask, node_to_present_cpumask[n])) {
  90                         node_set(n, *nodemsk);
  91                         nodes++;
  92                 }
  93         }
  94         return nodes;
  95 }
  96
  97 /**
  98  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
  99  * @nvecs:      The total number of vectors
 100  * @affd:       Description of the affinity requirements
 101  *
 102  * Returns the masks pointer or NULL if allocation failed.
 103  */
 104 struct cpumask *
 105 irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 106 {
 107         int n, nodes, cpus_per_vec, extra_vecs, curvec;
 108         int affv = nvecs - affd->pre_vectors - affd->post_vectors;
 109         int last_affv = affv + affd->pre_vectors;
 110         nodemask_t nodemsk = NODE_MASK_NONE;
 111         struct cpumask *masks;
 112         cpumask_var_t nmsk, *node_to_present_cpumask;
 113
 114         /*
 115          * If there aren't any vectors left after applying the pre/post
 116          * vectors don't bother with assigning affinity.
 117          */
 118         if (!affv)
 119                 return NULL;
 120
 121         if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 122                 return NULL;
 123
 124         masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
 125         if (!masks)
 126                 goto out;
 127
 128         node_to_present_cpumask = alloc_node_to_present_cpumask();
 129         if (!node_to_present_cpumask)
 130                 goto out;
 131
 132         /* Fill out vectors at the beginning that don't need affinity */
 133         for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 134                 cpumask_copy(masks + curvec, irq_default_affinity);
 135
 136         /* Stabilize the cpumasks */
 137         get_online_cpus();
 138         build_node_to_present_cpumask(node_to_present_cpumask);
 139         nodes = get_nodes_in_cpumask(node_to_present_cpumask, cpu_present_mask,
 140                                      &nodemsk);
 141
 142         /*
 143          * If the number of nodes in the mask is greater than or equal the
 144          * number of vectors we just spread the vectors across the nodes.
 145          */
 146         if (affv <= nodes) {
 147                 for_each_node_mask(n, nodemsk) {
 148                         cpumask_copy(masks + curvec,
 149                                      node_to_present_cpumask[n]);
 150                         if (++curvec == last_affv)
 151                                 break;
 152                 }
 153                 goto done;
 154         }
 155
 156         for_each_node_mask(n, nodemsk) {
 157                 int ncpus, v, vecs_to_assign, vecs_per_node;
 158
 159                 /* Spread the vectors per node */
 160                 vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
 161
 162                 /* Get the cpus on this node which are in the mask */
 163                 cpumask_and(nmsk, cpu_present_mask, node_to_present_cpumask[n]);
 164
 165                 /* Calculate the number of cpus per vector */
 166                 ncpus = cpumask_weight(nmsk);
 167                 vecs_to_assign = min(vecs_per_node, ncpus);
 168
 169                 /* Account for rounding errors */
 170                 extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
 171
 172                 for (v = 0; curvec < last_affv && v < vecs_to_assign;
 173                      curvec++, v++) {
 174                         cpus_per_vec = ncpus / vecs_to_assign;
 175
 176                         /* Account for extra vectors to compensate rounding errors */
 177                         if (extra_vecs) {
 178                                 cpus_per_vec++;
 179                                 --extra_vecs;
 180                         }
 181                         irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
 182                 }
 183
 184                 if (curvec >= last_affv)
 185                         break;
 186                 --nodes;
 187         }
 188
 189 done:
 190         put_online_cpus();
 191
 192         /* Fill out vectors at the end that don't need affinity */
 193         for (; curvec < nvecs; curvec++)
 194                 cpumask_copy(masks + curvec, irq_default_affinity);
 195         free_node_to_present_cpumask(node_to_present_cpumask);
 196 out:
 197         free_cpumask_var(nmsk);
 198         return masks;
 199 }
 200
 201 /**
 202  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
 203  * @minvec:     The minimum number of vectors available
 204  * @maxvec:     The maximum number of vectors available
 205  * @affd:       Description of the affinity requirements
 206  */
 207 int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd)
 208 {
 209         int resv = affd->pre_vectors + affd->post_vectors;
 210         int vecs = maxvec - resv;
 211         int ret;
 212
 213         if (resv > minvec)
 214                 return 0;
 215
 216         get_online_cpus();
 217         ret = min_t(int, cpumask_weight(cpu_present_mask), vecs) + resv;
 218         put_online_cpus();
 219         return ret;
 220 }