[tip: irq/core] genirq/affinity: Move group_cpus_evenly() into lib/
From: tip-bot2 for Ming Lei
Date: Tue Jan 17 2023 - 13:19:30 EST
The following commit has been merged into the irq/core branch of tip:
Commit-ID: f7b3ea8cf72f3d6060fe08e461805181e7450a13
Gitweb: https://git.kernel.org/tip/f7b3ea8cf72f3d6060fe08e461805181e7450a13
Author: Ming Lei <ming.lei@xxxxxxxxxx>
AuthorDate: Tue, 27 Dec 2022 10:29:04 +08:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 17 Jan 2023 18:50:06 +01:00
genirq/affinity: Move group_cpus_evenly() into lib/
group_cpus_evenly() has become a generic function which can be used for
other subsystems than the interrupt subsystem, so move it into lib/.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
Link: https://lore.kernel.org/r/20221227022905.352674-6-ming.lei@xxxxxxxxxx
---
MAINTAINERS | 2 +-
include/linux/group_cpus.h | 14 +-
kernel/irq/affinity.c | 398 +----------------------------------
lib/Makefile | 2 +-
lib/group_cpus.c | 427 ++++++++++++++++++++++++++++++++++++-
5 files changed, 446 insertions(+), 397 deletions(-)
create mode 100644 include/linux/group_cpus.h
create mode 100644 lib/group_cpus.c
diff --git a/MAINTAINERS b/MAINTAINERS
index a36df9e..9a07bd4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10935,6 +10935,8 @@ L: linux-kernel@xxxxxxxxxxxxxxx
S: Maintained
T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core
F: kernel/irq/
+F: include/linux/group_cpus.h
+F: lib/group_cpus.c
IRQCHIP DRIVERS
M: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
diff --git a/include/linux/group_cpus.h b/include/linux/group_cpus.h
new file mode 100644
index 0000000..e42807e
--- /dev/null
+++ b/include/linux/group_cpus.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2016 Thomas Gleixner.
+ * Copyright (C) 2016-2017 Christoph Hellwig.
+ */
+
+#ifndef __LINUX_GROUP_CPUS_H
+#define __LINUX_GROUP_CPUS_H
+#include <linux/kernel.h>
+#include <linux/cpu.h>
+
+struct cpumask *group_cpus_evenly(unsigned int numgrps);
+
+#endif
diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index 5408333..44a4eba 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -7,403 +7,7 @@
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/cpu.h>
-#include <linux/sort.h>
-
-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;
-}
-
-/*
- * build affinity in two stages for each group, and try to put close CPUs
- * in viewpoint of CPU and NUMA locality into same group, and we run
- * two-stage grouping:
- *
- * 1) allocate present CPUs on these groups evenly first
- * 2) allocate other possible CPUs on these groups evenly
- */
-static 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;
-
- /* Stabilize the cpumasks */
- cpus_read_lock();
- build_node_to_cpumask(node_to_cpumask);
-
- /* grouping present CPUs first */
- ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
- cpu_present_mask, 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, cpu_present_mask);
- ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
- npresmsk, nmsk, masks);
- if (ret >= 0)
- nr_others = ret;
-
- fail_build_affinity:
- cpus_read_unlock();
-
- 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;
-}
+#include <linux/group_cpus.h>
static void default_calc_sets(struct irq_affinity *affd, unsigned int affvecs)
{
diff --git a/lib/Makefile b/lib/Makefile
index 4d9461b..a4665a8 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -353,6 +353,8 @@ obj-$(CONFIG_SBITMAP) += sbitmap.o
obj-$(CONFIG_PARMAN) += parman.o
+obj-y += group_cpus.o
+
# GCC library routines
obj-$(CONFIG_GENERIC_LIB_ASHLDI3) += ashldi3.o
obj-$(CONFIG_GENERIC_LIB_ASHRDI3) += ashrdi3.o
diff --git a/lib/group_cpus.c b/lib/group_cpus.c
new file mode 100644
index 0000000..99f08c6
--- /dev/null
+++ b/lib/group_cpus.c
@@ -0,0 +1,427 @@
+// 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>
+
+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;
+}
+
+#ifdef CONFIG_SMP
+/**
+ * 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;
+
+ /* Stabilize the cpumasks */
+ cpus_read_lock();
+ build_node_to_cpumask(node_to_cpumask);
+
+ /* grouping present CPUs first */
+ ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
+ cpu_present_mask, 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, cpu_present_mask);
+ ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
+ npresmsk, nmsk, masks);
+ if (ret >= 0)
+ nr_others = ret;
+
+ fail_build_affinity:
+ cpus_read_unlock();
+
+ 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
+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