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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /lib/group_cpus.c | |
parent | Initial commit. (diff) | |
download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | lib/group_cpus.c | 439 |
1 files changed, 439 insertions, 0 deletions
diff --git a/lib/group_cpus.c b/lib/group_cpus.c new file mode 100644 index 0000000000..ee272c4cef --- /dev/null +++ b/lib/group_cpus.c @@ -0,0 +1,439 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2016 Thomas Gleixner. + * Copyright (C) 2016-2017 Christoph Hellwig. + */ +#include <linux/kernel.h> +#include <linux/slab.h> +#include <linux/cpu.h> +#include <linux/sort.h> +#include <linux/group_cpus.h> + +#ifdef CONFIG_SMP + +static void grp_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk, + unsigned int cpus_per_grp) +{ + const struct cpumask *siblmsk; + int cpu, sibl; + + for ( ; cpus_per_grp > 0; ) { + cpu = cpumask_first(nmsk); + + /* Should not happen, but I'm too lazy to think about it */ + if (cpu >= nr_cpu_ids) + return; + + cpumask_clear_cpu(cpu, nmsk); + cpumask_set_cpu(cpu, irqmsk); + cpus_per_grp--; + + /* If the cpu has siblings, use them first */ + siblmsk = topology_sibling_cpumask(cpu); + for (sibl = -1; cpus_per_grp > 0; ) { + sibl = cpumask_next(sibl, siblmsk); + if (sibl >= nr_cpu_ids) + break; + if (!cpumask_test_and_clear_cpu(sibl, nmsk)) + continue; + cpumask_set_cpu(sibl, irqmsk); + cpus_per_grp--; + } + } +} + +static cpumask_var_t *alloc_node_to_cpumask(void) +{ + cpumask_var_t *masks; + int node; + + masks = kcalloc(nr_node_ids, sizeof(cpumask_var_t), GFP_KERNEL); + if (!masks) + return NULL; + + for (node = 0; node < nr_node_ids; node++) { + if (!zalloc_cpumask_var(&masks[node], GFP_KERNEL)) + goto out_unwind; + } + + return masks; + +out_unwind: + while (--node >= 0) + free_cpumask_var(masks[node]); + kfree(masks); + return NULL; +} + +static void free_node_to_cpumask(cpumask_var_t *masks) +{ + int node; + + for (node = 0; node < nr_node_ids; node++) + free_cpumask_var(masks[node]); + kfree(masks); +} + +static void build_node_to_cpumask(cpumask_var_t *masks) +{ + int cpu; + + for_each_possible_cpu(cpu) + cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]); +} + +static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask, + const struct cpumask *mask, nodemask_t *nodemsk) +{ + int n, nodes = 0; + + /* Calculate the number of nodes in the supplied affinity mask */ + for_each_node(n) { + if (cpumask_intersects(mask, node_to_cpumask[n])) { + node_set(n, *nodemsk); + nodes++; + } + } + return nodes; +} + +struct node_groups { + unsigned id; + + union { + unsigned ngroups; + unsigned ncpus; + }; +}; + +static int ncpus_cmp_func(const void *l, const void *r) +{ + const struct node_groups *ln = l; + const struct node_groups *rn = r; + + return ln->ncpus - rn->ncpus; +} + +/* + * Allocate group number for each node, so that for each node: + * + * 1) the allocated number is >= 1 + * + * 2) the allocated number is <= active CPU number of this node + * + * The actual allocated total groups may be less than @numgrps when + * active total CPU number is less than @numgrps. + * + * Active CPUs means the CPUs in '@cpu_mask AND @node_to_cpumask[]' + * for each node. + */ +static void alloc_nodes_groups(unsigned int numgrps, + cpumask_var_t *node_to_cpumask, + const struct cpumask *cpu_mask, + const nodemask_t nodemsk, + struct cpumask *nmsk, + struct node_groups *node_groups) +{ + unsigned n, remaining_ncpus = 0; + + for (n = 0; n < nr_node_ids; n++) { + node_groups[n].id = n; + node_groups[n].ncpus = UINT_MAX; + } + + for_each_node_mask(n, nodemsk) { + unsigned ncpus; + + cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]); + ncpus = cpumask_weight(nmsk); + + if (!ncpus) + continue; + remaining_ncpus += ncpus; + node_groups[n].ncpus = ncpus; + } + + numgrps = min_t(unsigned, remaining_ncpus, numgrps); + + sort(node_groups, nr_node_ids, sizeof(node_groups[0]), + ncpus_cmp_func, NULL); + + /* + * Allocate groups for each node according to the ratio of this + * node's nr_cpus to remaining un-assigned ncpus. 'numgrps' is + * bigger than number of active numa nodes. Always start the + * allocation from the node with minimized nr_cpus. + * + * This way guarantees that each active node gets allocated at + * least one group, and the theory is simple: over-allocation + * is only done when this node is assigned by one group, so + * other nodes will be allocated >= 1 groups, since 'numgrps' is + * bigger than number of numa nodes. + * + * One perfect invariant is that number of allocated groups for + * each node is <= CPU count of this node: + * + * 1) suppose there are two nodes: A and B + * ncpu(X) is CPU count of node X + * grps(X) is the group count allocated to node X via this + * algorithm + * + * ncpu(A) <= ncpu(B) + * ncpu(A) + ncpu(B) = N + * grps(A) + grps(B) = G + * + * grps(A) = max(1, round_down(G * ncpu(A) / N)) + * grps(B) = G - grps(A) + * + * both N and G are integer, and 2 <= G <= N, suppose + * G = N - delta, and 0 <= delta <= N - 2 + * + * 2) obviously grps(A) <= ncpu(A) because: + * + * if grps(A) is 1, then grps(A) <= ncpu(A) given + * ncpu(A) >= 1 + * + * otherwise, + * grps(A) <= G * ncpu(A) / N <= ncpu(A), given G <= N + * + * 3) prove how grps(B) <= ncpu(B): + * + * if round_down(G * ncpu(A) / N) == 0, vecs(B) won't be + * over-allocated, so grps(B) <= ncpu(B), + * + * otherwise: + * + * grps(A) = + * round_down(G * ncpu(A) / N) = + * round_down((N - delta) * ncpu(A) / N) = + * round_down((N * ncpu(A) - delta * ncpu(A)) / N) >= + * round_down((N * ncpu(A) - delta * N) / N) = + * cpu(A) - delta + * + * then: + * + * grps(A) - G >= ncpu(A) - delta - G + * => + * G - grps(A) <= G + delta - ncpu(A) + * => + * grps(B) <= N - ncpu(A) + * => + * grps(B) <= cpu(B) + * + * For nodes >= 3, it can be thought as one node and another big + * node given that is exactly what this algorithm is implemented, + * and we always re-calculate 'remaining_ncpus' & 'numgrps', and + * finally for each node X: grps(X) <= ncpu(X). + * + */ + for (n = 0; n < nr_node_ids; n++) { + unsigned ngroups, ncpus; + + if (node_groups[n].ncpus == UINT_MAX) + continue; + + WARN_ON_ONCE(numgrps == 0); + + ncpus = node_groups[n].ncpus; + ngroups = max_t(unsigned, 1, + numgrps * ncpus / remaining_ncpus); + WARN_ON_ONCE(ngroups > ncpus); + + node_groups[n].ngroups = ngroups; + + remaining_ncpus -= ncpus; + numgrps -= ngroups; + } +} + +static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps, + cpumask_var_t *node_to_cpumask, + const struct cpumask *cpu_mask, + struct cpumask *nmsk, struct cpumask *masks) +{ + unsigned int i, n, nodes, cpus_per_grp, extra_grps, done = 0; + unsigned int last_grp = numgrps; + unsigned int curgrp = startgrp; + nodemask_t nodemsk = NODE_MASK_NONE; + struct node_groups *node_groups; + + if (cpumask_empty(cpu_mask)) + return 0; + + nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk); + + /* + * If the number of nodes in the mask is greater than or equal the + * number of groups we just spread the groups across the nodes. + */ + if (numgrps <= nodes) { + for_each_node_mask(n, nodemsk) { + /* Ensure that only CPUs which are in both masks are set */ + cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]); + cpumask_or(&masks[curgrp], &masks[curgrp], nmsk); + if (++curgrp == last_grp) + curgrp = 0; + } + return numgrps; + } + + node_groups = kcalloc(nr_node_ids, + sizeof(struct node_groups), + GFP_KERNEL); + if (!node_groups) + return -ENOMEM; + + /* allocate group number for each node */ + alloc_nodes_groups(numgrps, node_to_cpumask, cpu_mask, + nodemsk, nmsk, node_groups); + for (i = 0; i < nr_node_ids; i++) { + unsigned int ncpus, v; + struct node_groups *nv = &node_groups[i]; + + if (nv->ngroups == UINT_MAX) + continue; + + /* Get the cpus on this node which are in the mask */ + cpumask_and(nmsk, cpu_mask, node_to_cpumask[nv->id]); + ncpus = cpumask_weight(nmsk); + if (!ncpus) + continue; + + WARN_ON_ONCE(nv->ngroups > ncpus); + + /* Account for rounding errors */ + extra_grps = ncpus - nv->ngroups * (ncpus / nv->ngroups); + + /* Spread allocated groups on CPUs of the current node */ + for (v = 0; v < nv->ngroups; v++, curgrp++) { + cpus_per_grp = ncpus / nv->ngroups; + + /* Account for extra groups to compensate rounding errors */ + if (extra_grps) { + cpus_per_grp++; + --extra_grps; + } + + /* + * wrapping has to be considered given 'startgrp' + * may start anywhere + */ + if (curgrp >= last_grp) + curgrp = 0; + grp_spread_init_one(&masks[curgrp], nmsk, + cpus_per_grp); + } + done += nv->ngroups; + } + kfree(node_groups); + return done; +} + +/** + * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality + * @numgrps: number of groups + * + * Return: cpumask array if successful, NULL otherwise. And each element + * includes CPUs assigned to this group + * + * Try to put close CPUs from viewpoint of CPU and NUMA locality into + * same group, and run two-stage grouping: + * 1) allocate present CPUs on these groups evenly first + * 2) allocate other possible CPUs on these groups evenly + * + * We guarantee in the resulted grouping that all CPUs are covered, and + * no same CPU is assigned to multiple groups + */ +struct cpumask *group_cpus_evenly(unsigned int numgrps) +{ + unsigned int curgrp = 0, nr_present = 0, nr_others = 0; + cpumask_var_t *node_to_cpumask; + cpumask_var_t nmsk, npresmsk; + int ret = -ENOMEM; + struct cpumask *masks = NULL; + + if (!zalloc_cpumask_var(&nmsk, GFP_KERNEL)) + return NULL; + + if (!zalloc_cpumask_var(&npresmsk, GFP_KERNEL)) + goto fail_nmsk; + + node_to_cpumask = alloc_node_to_cpumask(); + if (!node_to_cpumask) + goto fail_npresmsk; + + masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); + if (!masks) + goto fail_node_to_cpumask; + + build_node_to_cpumask(node_to_cpumask); + + /* + * Make a local cache of 'cpu_present_mask', so the two stages + * spread can observe consistent 'cpu_present_mask' without holding + * cpu hotplug lock, then we can reduce deadlock risk with cpu + * hotplug code. + * + * Here CPU hotplug may happen when reading `cpu_present_mask`, and + * we can live with the case because it only affects that hotplug + * CPU is handled in the 1st or 2nd stage, and either way is correct + * from API user viewpoint since 2-stage spread is sort of + * optimization. + */ + cpumask_copy(npresmsk, data_race(cpu_present_mask)); + + /* grouping present CPUs first */ + ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask, + npresmsk, nmsk, masks); + if (ret < 0) + goto fail_build_affinity; + nr_present = ret; + + /* + * Allocate non present CPUs starting from the next group to be + * handled. If the grouping of present CPUs already exhausted the + * group space, assign the non present CPUs to the already + * allocated out groups. + */ + if (nr_present >= numgrps) + curgrp = 0; + else + curgrp = nr_present; + cpumask_andnot(npresmsk, cpu_possible_mask, npresmsk); + ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask, + npresmsk, nmsk, masks); + if (ret >= 0) + nr_others = ret; + + fail_build_affinity: + if (ret >= 0) + WARN_ON(nr_present + nr_others < numgrps); + + fail_node_to_cpumask: + free_node_to_cpumask(node_to_cpumask); + + fail_npresmsk: + free_cpumask_var(npresmsk); + + fail_nmsk: + free_cpumask_var(nmsk); + if (ret < 0) { + kfree(masks); + return NULL; + } + return masks; +} +#else /* CONFIG_SMP */ +struct cpumask *group_cpus_evenly(unsigned int numgrps) +{ + struct cpumask *masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL); + + if (!masks) + return NULL; + + /* assign all CPUs(cpu 0) to the 1st group only */ + cpumask_copy(&masks[0], cpu_possible_mask); + return masks; +} +#endif /* CONFIG_SMP */ +EXPORT_SYMBOL_GPL(group_cpus_evenly); |