kernel/irq/affinity.c

   1
   2 #include <linux/interrupt.h>
   3 #include <linux/kernel.h>
   4 #include <linux/slab.h>
   5 #include <linux/cpu.h>
   6
   7 static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
   8                                 int cpus_per_vec)
   9 {
  10         const struct cpumask *siblmsk;
  11         int cpu, sibl;
  12
  13         for ( ; cpus_per_vec > 0; ) {
  14                 cpu = cpumask_first(nmsk);
  15
  16                 /* Should not happen, but I'm too lazy to think about it */
  17                 if (cpu >= nr_cpu_ids)
  18                         return;
  19
  20                 cpumask_clear_cpu(cpu, nmsk);
  21                 cpumask_set_cpu(cpu, irqmsk);
  22                 cpus_per_vec--;
  23
  24                 /* If the cpu has siblings, use them first */
  25                 siblmsk = topology_sibling_cpumask(cpu);
  26                 for (sibl = -1; cpus_per_vec > 0; ) {
  27                         sibl = cpumask_next(sibl, siblmsk);
  28                         if (sibl >= nr_cpu_ids)
  29                                 break;
  30                         if (!cpumask_test_and_clear_cpu(sibl, nmsk))
  31                                 continue;
  32                         cpumask_set_cpu(sibl, irqmsk);
  33                         cpus_per_vec--;
  34                 }
  35         }
  36 }
  37
  38 static int get_nodes_in_cpumask(const struct cpumask *mask, nodemask_t *nodemsk)
  39 {
  40         int n, nodes = 0;
  41
  42         /* Calculate the number of nodes in the supplied affinity mask */
  43         for_each_online_node(n) {
  44                 if (cpumask_intersects(mask, cpumask_of_node(n))) {
  45                         node_set(n, *nodemsk);
  46                         nodes++;
  47                 }
  48         }
  49         return nodes;
  50 }
  51
  52 /**
  53  * irq_create_affinity_masks - Create affinity masks for multiqueue spreading
  54  * @nvecs:      The total number of vectors
  55  * @affd:       Description of the affinity requirements
  56  *
  57  * Returns the masks pointer or NULL if allocation failed.
  58  */
  59 struct cpumask *
  60 irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
  61 {
  62         int n, nodes, cpus_per_vec, extra_vecs, curvec;
  63         int affv = nvecs - affd->pre_vectors - affd->post_vectors;
  64         int last_affv = affv + affd->pre_vectors;
  65         nodemask_t nodemsk = NODE_MASK_NONE;
  66         struct cpumask *masks;
  67         cpumask_var_t nmsk;
  68
  69         if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
  70                 return NULL;
  71
  72         masks = kcalloc(nvecs, sizeof(*masks), GFP_KERNEL);
  73         if (!masks)
  74                 goto out;
  75
  76         /* Fill out vectors at the beginning that don't need affinity */
  77         for (curvec = 0; curvec < affd->pre_vectors; curvec++)
  78                 cpumask_copy(masks + curvec, irq_default_affinity);
  79
  80         /* Stabilize the cpumasks */
  81         get_online_cpus();
  82         nodes = get_nodes_in_cpumask(cpu_online_mask, &nodemsk);
  83
  84         /*
  85          * If the number of nodes in the mask is greater than or equal the
  86          * number of vectors we just spread the vectors across the nodes.
  87          */
  88         if (affv <= nodes) {
  89                 for_each_node_mask(n, nodemsk) {
  90                         cpumask_copy(masks + curvec, cpumask_of_node(n));
  91                         if (++curvec == last_affv)
  92                                 break;
  93                 }
  94                 goto done;
  95         }
  96
  97         for_each_node_mask(n, nodemsk) {
  98                 int ncpus, v, vecs_to_assign, vecs_per_node;
  99
 100                 /* Spread the vectors per node */
 101                 vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
 102
 103                 /* Get the cpus on this node which are in the mask */
 104                 cpumask_and(nmsk, cpu_online_mask, cpumask_of_node(n));
 105
 106                 /* Calculate the number of cpus per vector */
 107                 ncpus = cpumask_weight(nmsk);
 108                 vecs_to_assign = min(vecs_per_node, ncpus);
 109
 110                 /* Account for rounding errors */
 111                 extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
 112
 113                 for (v = 0; curvec < last_affv && v < vecs_to_assign;
 114                      curvec++, v++) {
 115                         cpus_per_vec = ncpus / vecs_to_assign;
 116
 117                         /* Account for extra vectors to compensate rounding errors */
 118                         if (extra_vecs) {
 119                                 cpus_per_vec++;
 120                                 --extra_vecs;
 121                         }
 122                         irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
 123                 }
 124
 125                 if (curvec >= last_affv)
 126                         break;
 127                 --nodes;
 128         }
 129
 130 done:
 131         put_online_cpus();
 132
 133         /* Fill out vectors at the end that don't need affinity */
 134         for (; curvec < nvecs; curvec++)
 135                 cpumask_copy(masks + curvec, irq_default_affinity);
 136 out:
 137         free_cpumask_var(nmsk);
 138         return masks;
 139 }
 140
 141 /**
 142  * irq_calc_affinity_vectors - Calculate the optimal number of vectors
 143  * @maxvec:     The maximum number of vectors available
 144  * @affd:       Description of the affinity requirements
 145  */
 146 int irq_calc_affinity_vectors(int maxvec, const struct irq_affinity *affd)
 147 {
 148         int resv = affd->pre_vectors + affd->post_vectors;
 149         int vecs = maxvec - resv;
 150         int cpus;
 151
 152         /* Stabilize the cpumasks */
 153         get_online_cpus();
 154         cpus = cpumask_weight(cpu_online_mask);
 155         put_online_cpus();
 156
 157         return min(cpus, vecs) + resv;
 158 }