440 lines
11 KiB
C
440 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2016 Thomas Gleixner.
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* Copyright (C) 2016-2017 Christoph Hellwig.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/cpu.h>
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#include <linux/sort.h>
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#include <linux/group_cpus.h>
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#ifdef CONFIG_SMP
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static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
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unsigned int cpus_per_grp)
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{
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const struct cpumask *siblmsk;
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int cpu, sibl;
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for ( ; cpus_per_grp > 0; ) {
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cpu = cpumask_first(nmsk);
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/* Should not happen, but I'm too lazy to think about it */
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if (cpu >= nr_cpu_ids)
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return;
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cpumask_clear_cpu(cpu, nmsk);
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cpumask_set_cpu(cpu, irqmsk);
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cpus_per_grp--;
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/* If the cpu has siblings, use them first */
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siblmsk = topology_sibling_cpumask(cpu);
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for (sibl = -1; cpus_per_grp > 0; ) {
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sibl = cpumask_next(sibl, siblmsk);
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if (sibl >= nr_cpu_ids)
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break;
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if (!cpumask_test_and_clear_cpu(sibl, nmsk))
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continue;
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cpumask_set_cpu(sibl, irqmsk);
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cpus_per_grp--;
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}
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}
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}
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static cpumask_var_t *alloc_node_to_cpumask(void)
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{
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cpumask_var_t *masks;
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int node;
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masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL);
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if (!masks)
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return NULL;
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for (node = 0; node < nr_node_ids; node++) {
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if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL))
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goto out_unwind;
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}
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return masks;
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out_unwind:
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while (--node >= 0)
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free_cpumask_var(masks[node]);
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kfree(masks);
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return NULL;
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}
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static void free_node_to_cpumask(cpumask_var_t *masks)
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{
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int node;
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for (node = 0; node < nr_node_ids; node++)
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free_cpumask_var(masks[node]);
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kfree(masks);
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}
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static void build_node_to_cpumask(cpumask_var_t *masks)
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{
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int cpu;
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for_each_possible_cpu(cpu)
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cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
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}
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static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
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const struct cpumask *mask, nodemask_t *nodemsk)
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{
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int n, nodes = 0;
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/* Calculate the number of nodes in the supplied affinity mask */
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for_each_node(n) {
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if (cpumask_intersects(mask, node_to_cpumask[n])) {
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node_set(n, *nodemsk);
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nodes++;
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}
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}
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return nodes;
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}
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struct node_groups {
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unsigned id;
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union {
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unsigned ngroups;
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unsigned ncpus;
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};
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};
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static int ncpus_cmp_func(const void *l, const void *r)
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{
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const struct node_groups *ln = l;
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const struct node_groups *rn = r;
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return ln->ncpus - rn->ncpus;
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}
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/*
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* Allocate group number for each node, so that for each node:
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*
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* 1) the allocated number is >= 1
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*
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* 2) the allocated number is <= active CPU number of this node
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*
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* The actual allocated total groups may be less than @numgrps when
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* active total CPU number is less than @numgrps.
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*
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* Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]'
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* for each node.
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*/
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static void alloc_nodes_groups(unsigned int numgrps,
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cpumask_var_t *node_to_cpumask,
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const struct cpumask *cpu_mask,
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const nodemask_t nodemsk,
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struct cpumask *nmsk,
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struct node_groups *node_groups)
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{
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unsigned n, remaining_ncpus = 0;
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for (n = 0; n < nr_node_ids; n++) {
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node_groups[n].id = n;
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node_groups[n].ncpus = UINT_MAX;
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}
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for_each_node_mask(n, nodemsk) {
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unsigned ncpus;
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cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
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ncpus = cpumask_weight(nmsk);
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if (!ncpus)
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continue;
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remaining_ncpus += ncpus;
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node_groups[n].ncpus = ncpus;
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}
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numgrps = min_t(unsigned, remaining_ncpus, numgrps);
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sort(node_groups, nr_node_ids, sizeof(node_groups[0]),
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ncpus_cmp_func, NULL);
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/*
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* Allocate groups for each node according to the ratio of this
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* node's nr_cpus to remaining un-assigned ncpus. 'numgrps' is
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* bigger than number of active numa nodes. Always start the
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* allocation from the node with minimized nr_cpus.
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*
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* This way guarantees that each active node gets allocated at
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* least one group, and the theory is simple: over-allocation
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* is only done when this node is assigned by one group, so
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* other nodes will be allocated >= 1 groups, since 'numgrps' is
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* bigger than number of numa nodes.
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*
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* One perfect invariant is that number of allocated groups for
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* each node is <= CPU count of this node:
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*
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* 1) suppose there are two nodes: A and B
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* ncpu(X) is CPU count of node X
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* grps(X) is the group count allocated to node X via this
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* algorithm
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*
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* ncpu(A) <= ncpu(B)
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* ncpu(A) + ncpu(B) = N
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* grps(A) + grps(B) = G
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*
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* grps(A) = max(1, round_down(G * ncpu(A) / N))
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* grps(B) = G - grps(A)
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*
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* both N and G are integer, and 2 <= G <= N, suppose
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* G = N - delta, and 0 <= delta <= N - 2
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*
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* 2) obviously grps(A) <= ncpu(A) because:
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*
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* if grps(A) is 1, then grps(A) <= ncpu(A) given
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* ncpu(A) >= 1
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*
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* otherwise,
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* grps(A) <= G * ncpu(A) / N <= ncpu(A), given G <= N
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*
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* 3) prove how grps(B) <= ncpu(B):
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*
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* if round_down(G * ncpu(A) / N) == 0, vecs(B) won't be
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* over-allocated, so grps(B) <= ncpu(B),
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*
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* otherwise:
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*
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* grps(A) =
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* round_down(G * ncpu(A) / N) =
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* round_down((N - delta) * ncpu(A) / N) =
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* round_down((N * ncpu(A) - delta * ncpu(A)) / N) >=
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* round_down((N * ncpu(A) - delta * N) / N) =
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* cpu(A) - delta
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*
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* then:
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*
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* grps(A) - G >= ncpu(A) - delta - G
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* =>
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* G - grps(A) <= G + delta - ncpu(A)
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* =>
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* grps(B) <= N - ncpu(A)
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* =>
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* grps(B) <= cpu(B)
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*
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* For nodes >= 3, it can be thought as one node and another big
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* node given that is exactly what this algorithm is implemented,
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* and we always re-calculate 'remaining_ncpus' & 'numgrps', and
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* finally for each node X: grps(X) <= ncpu(X).
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*
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*/
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for (n = 0; n < nr_node_ids; n++) {
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unsigned ngroups, ncpus;
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if (node_groups[n].ncpus == UINT_MAX)
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continue;
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WARN_ON_ONCE(numgrps == 0);
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ncpus = node_groups[n].ncpus;
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ngroups = max_t(unsigned, 1,
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numgrps * ncpus / remaining_ncpus);
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WARN_ON_ONCE(ngroups > ncpus);
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node_groups[n].ngroups = ngroups;
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remaining_ncpus -= ncpus;
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numgrps -= ngroups;
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}
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}
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static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
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cpumask_var_t *node_to_cpumask,
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const struct cpumask *cpu_mask,
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struct cpumask *nmsk, struct cpumask *masks)
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{
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unsigned int i, n, nodes, cpus_per_grp, extra_grps, done = 0;
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unsigned int last_grp = numgrps;
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unsigned int curgrp = startgrp;
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nodemask_t nodemsk = NODE_MASK_NONE;
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struct node_groups *node_groups;
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if (cpumask_empty(cpu_mask))
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return 0;
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nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);
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/*
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* If the number of nodes in the mask is greater than or equal the
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* number of groups we just spread the groups across the nodes.
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*/
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if (numgrps <= nodes) {
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for_each_node_mask(n, nodemsk) {
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/* Ensure that only CPUs which are in both masks are set */
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cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
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cpumask_or(&masks[curgrp], &masks[curgrp], nmsk);
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if (++curgrp == last_grp)
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curgrp = 0;
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}
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return numgrps;
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}
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node_groups = kcalloc(nr_node_ids,
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sizeof(struct node_groups),
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GFP_KERNEL);
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if (!node_groups)
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return -ENOMEM;
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/* allocate group number for each node */
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alloc_nodes_groups(numgrps, node_to_cpumask, cpu_mask,
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nodemsk, nmsk, node_groups);
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for (i = 0; i < nr_node_ids; i++) {
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unsigned int ncpus, v;
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struct node_groups *nv = &node_groups[i];
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if (nv->ngroups == UINT_MAX)
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continue;
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/* Get the cpus on this node which are in the mask */
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cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]);
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ncpus = cpumask_weight(nmsk);
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if (!ncpus)
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continue;
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WARN_ON_ONCE(nv->ngroups > ncpus);
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/* Account for rounding errors */
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extra_grps = ncpus - nv->ngroups * (ncpus / nv->ngroups);
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/* Spread allocated groups on CPUs of the current node */
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for (v = 0; v < nv->ngroups; v++, curgrp++) {
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cpus_per_grp = ncpus / nv->ngroups;
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/* Account for extra groups to compensate rounding errors */
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if (extra_grps) {
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cpus_per_grp++;
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--extra_grps;
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}
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/*
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* wrapping has to be considered given 'startgrp'
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* may start anywhere
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*/
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if (curgrp >= last_grp)
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curgrp = 0;
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grp_spread_init_one(&masks[curgrp], nmsk,
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cpus_per_grp);
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}
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done += nv->ngroups;
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}
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kfree(node_groups);
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return done;
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}
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/**
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* group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
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* @numgrps: number of groups
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*
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* Return: cpumask array if successful, NULL otherwise. And each element
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* includes CPUs assigned to this group
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*
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* Try to put close CPUs from viewpoint of CPU and NUMA locality into
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* same group, and run two-stage grouping:
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* 1) allocate present CPUs on these groups evenly first
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* 2) allocate other possible CPUs on these groups evenly
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*
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* We guarantee in the resulted grouping that all CPUs are covered, and
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* no same CPU is assigned to multiple groups
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*/
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struct cpumask *group_cpus_evenly(unsigned int numgrps)
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{
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unsigned int curgrp = 0, nr_present = 0, nr_others = 0;
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cpumask_var_t *node_to_cpumask;
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cpumask_var_t nmsk, npresmsk;
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int ret = -ENOMEM;
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struct cpumask *masks = NULL;
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if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL))
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return NULL;
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if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL))
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goto fail_nmsk;
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node_to_cpumask = alloc_node_to_cpumask();
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if (!node_to_cpumask)
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goto fail_npresmsk;
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masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL);
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if (!masks)
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goto fail_node_to_cpumask;
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build_node_to_cpumask(node_to_cpumask);
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/*
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* Make a local cache of 'cpu_present_mask', so the two stages
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* spread can observe consistent 'cpu_present_mask' without holding
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* cpu hotplug lock, then we can reduce deadlock risk with cpu
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* hotplug code.
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*
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* Here CPU hotplug may happen when reading `cpu_present_mask`, and
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* we can live with the case because it only affects that hotplug
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* CPU is handled in the 1st or 2nd stage, and either way is correct
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* from API user viewpoint since 2-stage spread is sort of
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* optimization.
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*/
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cpumask_copy(npresmsk, data_race(cpu_present_mask));
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/* grouping present CPUs first */
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ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
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npresmsk, nmsk, masks);
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if (ret < 0)
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goto fail_build_affinity;
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nr_present = ret;
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/*
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* Allocate non present CPUs starting from the next group to be
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* handled. If the grouping of present CPUs already exhausted the
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* group space, assign the non present CPUs to the already
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* allocated out groups.
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*/
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if (nr_present >= numgrps)
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curgrp = 0;
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else
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curgrp = nr_present;
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cpumask_andnot(npresmsk, cpu_possible_mask, npresmsk);
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ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
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npresmsk, nmsk, masks);
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if (ret >= 0)
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nr_others = ret;
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fail_build_affinity:
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if (ret >= 0)
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WARN_ON(nr_present + nr_others < numgrps);
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fail_node_to_cpumask:
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free_node_to_cpumask(node_to_cpumask);
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fail_npresmsk:
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free_cpumask_var(npresmsk);
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fail_nmsk:
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free_cpumask_var(nmsk);
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if (ret < 0) {
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kfree(masks);
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return NULL;
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}
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return masks;
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}
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#else /* CONFIG_SMP */
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struct cpumask *group_cpus_evenly(unsigned int numgrps)
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{
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struct cpumask *masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL);
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if (!masks)
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return NULL;
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/* assign all CPUs(cpu 0) to the 1st group only */
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cpumask_copy(&masks[0], cpu_possible_mask);
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return masks;
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}
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#endif /* CONFIG_SMP */
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EXPORT_SYMBOL_GPL(group_cpus_evenly);
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