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;
  41
  42         /* Calculate the number of nodes in the supplied affinity mask */
  43         for (n = 0, nodes = 0; n < num_online_nodes(); 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  * @affinity:           The affinity mask to spread. If NULL cpu_online_mask
  55  *                      is used
  56  * @nvecs:              The number of vectors
  57  *
  58  * Returns the masks pointer or NULL if allocation failed.
  59  */
  60 struct cpumask *irq_create_affinity_masks(const struct cpumask *affinity,
  61                                           int nvec)
  62 {
  63         int n, nodes, vecs_per_node, cpus_per_vec, extra_vecs, curvec = 0;
  64         nodemask_t nodemsk = NODE_MASK_NONE;
  65         struct cpumask *masks;
  66         cpumask_var_t nmsk;
  67
  68         if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
  69                 return NULL;
  70
  71         masks = kzalloc(nvec * sizeof(*masks), GFP_KERNEL);
  72         if (!masks)
  73                 goto out;
  74
  75         /* Stabilize the cpumasks */
  76         get_online_cpus();
  77         /* If the supplied affinity mask is NULL, use cpu online mask */
  78         if (!affinity)
  79                 affinity = cpu_online_mask;
  80
  81         nodes = get_nodes_in_cpumask(affinity, &nodemsk);
  82
  83         /*
  84          * If the number of nodes in the mask is less than or equal the
  85          * number of vectors we just spread the vectors across the nodes.
  86          */
  87         if (nvec <= nodes) {
  88                 for_each_node_mask(n, nodemsk) {
  89                         cpumask_copy(masks + curvec, cpumask_of_node(n));
  90                         if (++curvec == nvec)
  91                                 break;
  92                 }
  93                 goto outonl;
  94         }
  95
  96         /* Spread the vectors per node */
  97         vecs_per_node = nvec / nodes;
  98         /* Account for rounding errors */
  99         extra_vecs = nvec - (nodes * vecs_per_node);
 100
 101         for_each_node_mask(n, nodemsk) {
 102                 int ncpus, v, vecs_to_assign = vecs_per_node;
 103
 104                 /* Get the cpus on this node which are in the mask */
 105                 cpumask_and(nmsk, affinity, cpumask_of_node(n));
 106
 107                 /* Calculate the number of cpus per vector */
 108                 ncpus = cpumask_weight(nmsk);
 109
 110                 for (v = 0; curvec < nvec && v < vecs_to_assign; curvec++, v++) {
 111                         cpus_per_vec = ncpus / vecs_to_assign;
 112
 113                         /* Account for extra vectors to compensate rounding errors */
 114                         if (extra_vecs) {
 115                                 cpus_per_vec++;
 116                                 if (!--extra_vecs)
 117                                         vecs_per_node++;
 118                         }
 119                         irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
 120                 }
 121
 122                 if (curvec >= nvec)
 123                         break;
 124         }
 125
 126 outonl:
 127         put_online_cpus();
 128 out:
 129         free_cpumask_var(nmsk);
 130         return masks;
 131 }
 132
 133 /**
 134  * irq_calc_affinity_vectors - Calculate to optimal number of vectors for a given affinity mask
 135  * @affinity:           The affinity mask to spread. If NULL cpu_online_mask
 136  *                      is used
 137  * @maxvec:             The maximum number of vectors available
 138  */
 139 int irq_calc_affinity_vectors(const struct cpumask *affinity, int maxvec)
 140 {
 141         int cpus, ret;
 142
 143         /* Stabilize the cpumasks */
 144         get_online_cpus();
 145         /* If the supplied affinity mask is NULL, use cpu online mask */
 146         if (!affinity)
 147                 affinity = cpu_online_mask;
 148
 149         cpus = cpumask_weight(affinity);
 150         ret = (cpus < maxvec) ? cpus : maxvec;
 151
 152         put_online_cpus();
 153         return ret;
 154 }