kernel/irq/affinity.c

   1 /*
   2  * Copyright (C) 2016 Thomas Gleixner.
   3  * Copyright (C) 2016-2017 Christoph Hellwig.
   4  */
   5 #include <linux/interrupt.h>
   6 #include <linux/kernel.h>
   7 #include <linux/slab.h>
   8 #include <linux/cpu.h>
   9
  10 static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
  11                                 int cpus_per_vec)
  12 {
  13         const struct cpumask *siblmsk;
  14         int cpu, sibl;
  15
  16         for ( ; cpus_per_vec > 0; ) {
  17                 cpu = cpumask_first(nmsk);
  18
  19                 /* Should not happen, but I'm too lazy to think about it */
  20                 if (cpu >= nr_cpu_ids)
  21                         return;
  22
  23                 cpumask_clear_cpu(cpu, nmsk);
  24                 cpumask_set_cpu(cpu, irqmsk);
  25                 cpus_per_vec--;
  26
  27                 /* If the cpu has siblings, use them first */
  28                 siblmsk = topology_sibling_cpumask(cpu);
  29                 for (sibl = -1; cpus_per_vec > 0; ) {
  30                         sibl = cpumask_next(sibl, siblmsk);
  31                         if (sibl >= nr_cpu_ids)
  32                                 break;
  33                         if (!cpumask_test_and_clear_cpu(sibl, nmsk))
  34                                 continue;
  35                         cpumask_set_cpu(sibl, irqmsk);
  36                         cpus_per_vec--;
  37                 }
  38         }
  39 }
  40
  41 static cpumask_var_t *alloc_node_to_present_cpumask(void)
  42 {
  43         cpumask_var_t *masks;
  44         int node;
  45
  46         masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
  47         if (!masks)
  48                 return NULL;
  49
  50         for (node = 0; node < nr_node_ids; node++) {
  51                 if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
  52                         goto out_unwind;
  53         }
  54
  55         return masks;
  56
  57 out_unwind:
  58         while (--node >= 0)
  59                 free_cpumask_var(masks[node]);
  60         kfree(masks);
  61         return NULL;
  62 }
  63
  64 static void free_node_to_present_cpumask(cpumask_var_t *masks)
  65 {
  66         int node;
  67
  68         for (node = 0; node < nr_node_ids; node++)
  69                 free_cpumask_var(masks[node]);
  70         kfree(masks);
  71 }
  72
  73 static void build_node_to_present_cpumask(cpumask_var_t *masks)
  74 {
  75         int cpu;
  76
  77         for_each_present_cpu(cpu)
  78                 cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
  79 }
  80
  81 static int get_nodes_in_cpumask(cpumask_var_t *node_to_present_cpumask,
  82                                 const struct cpumask *mask, nodemask_t *nodemsk)
  83 {
  84         int n, nodes = 0;
  85
  86         /* Calculate the number of nodes in the supplied affinity mask */
  87         for_each_node(n) {
  88                 if (cpumask_intersects(mask, node_to_present_cpumask[n])) {
  89                         node_set(n, *nodemsk);
  90                         nodes++;
  91                 }
  92         }
  93         return nodes;
  94 }
  95
  96 /**
  97  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
  98  * @nvecs:      The total number of vectors
  99  * @affd:       Description of the affinity requirements
 100  *
 101  * Returns the masks pointer or NULL if allocation failed.
 102  */
 103 struct cpumask *
 104 irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 105 {
 106         int n, nodes, cpus_per_vec, extra_vecs, curvec;
 107         int affv = nvecs - affd->pre_vectors - affd->post_vectors;
 108         int last_affv = affv + affd->pre_vectors;
 109         nodemask_t nodemsk = NODE_MASK_NONE;
 110         struct cpumask *masks;
 111         cpumask_var_t nmsk, *node_to_present_cpumask;
 112
 113         /*
 114          * If there aren't any vectors left after applying the pre/post
 115          * vectors don't bother with assigning affinity.
 116          */
 117         if (!affv)
 118                 return NULL;
 119
 120         if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
 121                 return NULL;
 122
 123         masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
 124         if (!masks)
 125                 goto out;
 126
 127         node_to_present_cpumask = alloc_node_to_present_cpumask();
 128         if (!node_to_present_cpumask)
 129                 goto out;
 130
 131         /* Fill out vectors at the beginning that don't need affinity */
 132         for (curvec = 0; curvec < affd->pre_vectors; curvec++)
 133                 cpumask_copy(masks + curvec, irq_default_affinity);
 134
 135         /* Stabilize the cpumasks */
 136         get_online_cpus();
 137         build_node_to_present_cpumask(node_to_present_cpumask);
 138         nodes = get_nodes_in_cpumask(node_to_present_cpumask, cpu_present_mask,
 139                                      &nodemsk);
 140
 141         /*
 142          * If the number of nodes in the mask is greater than or equal the
 143          * number of vectors we just spread the vectors across the nodes.
 144          */
 145         if (affv <= nodes) {
 146                 for_each_node_mask(n, nodemsk) {
 147                         cpumask_copy(masks + curvec,
 148                                      node_to_present_cpumask[n]);
 149                         if (++curvec == last_affv)
 150                                 break;
 151                 }
 152                 goto done;
 153         }
 154
 155         for_each_node_mask(n, nodemsk) {
 156                 int ncpus, v, vecs_to_assign, vecs_per_node;
 157
 158                 /* Spread the vectors per node */
 159                 vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
 160
 161                 /* Get the cpus on this node which are in the mask */
 162                 cpumask_and(nmsk, cpu_present_mask, node_to_present_cpumask[n]);
 163
 164                 /* Calculate the number of cpus per vector */
 165                 ncpus = cpumask_weight(nmsk);
 166                 vecs_to_assign = min(vecs_per_node, ncpus);
 167
 168                 /* Account for rounding errors */
 169                 extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
 170
 171                 for (v = 0; curvec < last_affv && v < vecs_to_assign;
 172                      curvec++, v++) {
 173                         cpus_per_vec = ncpus / vecs_to_assign;
 174
 175                         /* Account for extra vectors to compensate rounding errors */
 176                         if (extra_vecs) {
 177                                 cpus_per_vec++;
 178                                 --extra_vecs;
 179                         }
 180                         irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
 181                 }
 182
 183                 if (curvec >= last_affv)
 184                         break;
 185                 --nodes;
 186         }
 187
 188 done:
 189         put_online_cpus();
 190
 191         /* Fill out vectors at the end that don't need affinity */
 192         for (; curvec < nvecs; curvec++)
 193                 cpumask_copy(masks + curvec, irq_default_affinity);
 194         free_node_to_present_cpumask(node_to_present_cpumask);
 195 out:
 196         free_cpumask_var(nmsk);
 197         return masks;
 198 }
 199
 200 /**
 201  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
 202  * @minvec:     The minimum number of vectors available
 203  * @maxvec:     The maximum number of vectors available
 204  * @affd:       Description of the affinity requirements
 205  */
 206 int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity *affd)
 207 {
 208         int resv = affd->pre_vectors + affd->post_vectors;
 209         int vecs = maxvec - resv;
 210         int ret;
 211
 212         if (resv > minvec)
 213                 return 0;
 214
 215         get_online_cpus();
 216         ret = min_t(int, cpumask_weight(cpu_present_mask), vecs) + resv;
 217         put_online_cpus();
 218         return ret;
 219 }