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Now that we have an iterator-based alternative for a very common case of using cpumask_local_spread for all cpus in a row, it's worth to mention that in comment to cpumask_local_spread(). Signed-off-by: Yury Norov <yury.norov@gmail.com> Reviewed-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
197 lines
5.3 KiB
C
197 lines
5.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/slab.h>
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#include <linux/kernel.h>
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#include <linux/bitops.h>
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#include <linux/cpumask.h>
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#include <linux/export.h>
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#include <linux/memblock.h>
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#include <linux/numa.h>
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/**
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* cpumask_next_wrap - helper to implement for_each_cpu_wrap
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* @n: the cpu prior to the place to search
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* @mask: the cpumask pointer
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* @start: the start point of the iteration
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* @wrap: assume @n crossing @start terminates the iteration
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*
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* Returns >= nr_cpu_ids on completion
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*
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* Note: the @wrap argument is required for the start condition when
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* we cannot assume @start is set in @mask.
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*/
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unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
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{
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unsigned int next;
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again:
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next = cpumask_next(n, mask);
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if (wrap && n < start && next >= start) {
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return nr_cpumask_bits;
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} else if (next >= nr_cpumask_bits) {
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wrap = true;
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n = -1;
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goto again;
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}
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return next;
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}
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EXPORT_SYMBOL(cpumask_next_wrap);
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/* These are not inline because of header tangles. */
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#ifdef CONFIG_CPUMASK_OFFSTACK
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/**
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* alloc_cpumask_var_node - allocate a struct cpumask on a given node
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* @mask: pointer to cpumask_var_t where the cpumask is returned
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* @flags: GFP_ flags
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*
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* Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
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* a nop returning a constant 1 (in <linux/cpumask.h>)
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* Returns TRUE if memory allocation succeeded, FALSE otherwise.
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*
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* In addition, mask will be NULL if this fails. Note that gcc is
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* usually smart enough to know that mask can never be NULL if
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* CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
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* too.
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*/
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bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
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{
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*mask = kmalloc_node(cpumask_size(), flags, node);
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#ifdef CONFIG_DEBUG_PER_CPU_MAPS
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if (!*mask) {
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printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
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dump_stack();
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}
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#endif
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return *mask != NULL;
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}
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EXPORT_SYMBOL(alloc_cpumask_var_node);
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/**
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* alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
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* @mask: pointer to cpumask_var_t where the cpumask is returned
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*
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* Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
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* a nop (in <linux/cpumask.h>).
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* Either returns an allocated (zero-filled) cpumask, or causes the
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* system to panic.
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*/
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void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
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{
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*mask = memblock_alloc(cpumask_size(), SMP_CACHE_BYTES);
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if (!*mask)
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panic("%s: Failed to allocate %u bytes\n", __func__,
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cpumask_size());
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}
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/**
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* free_cpumask_var - frees memory allocated for a struct cpumask.
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* @mask: cpumask to free
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*
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* This is safe on a NULL mask.
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*/
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void free_cpumask_var(cpumask_var_t mask)
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{
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kfree(mask);
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}
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EXPORT_SYMBOL(free_cpumask_var);
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/**
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* free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
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* @mask: cpumask to free
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*/
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void __init free_bootmem_cpumask_var(cpumask_var_t mask)
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{
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memblock_free(mask, cpumask_size());
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}
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#endif
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/**
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* cpumask_local_spread - select the i'th cpu based on NUMA distances
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* @i: index number
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* @node: local numa_node
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*
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* Returns online CPU according to a numa aware policy; local cpus are returned
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* first, followed by non-local ones, then it wraps around.
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*
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* For those who wants to enumerate all CPUs based on their NUMA distances,
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* i.e. call this function in a loop, like:
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*
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* for (i = 0; i < num_online_cpus(); i++) {
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* cpu = cpumask_local_spread(i, node);
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* do_something(cpu);
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* }
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*
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* There's a better alternative based on for_each()-like iterators:
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*
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* for_each_numa_hop_mask(mask, node) {
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* for_each_cpu_andnot(cpu, mask, prev)
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* do_something(cpu);
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* prev = mask;
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* }
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*
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* It's simpler and more verbose than above. Complexity of iterator-based
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* enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while
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* cpumask_local_spread() when called for each cpu is
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* O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)).
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*/
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unsigned int cpumask_local_spread(unsigned int i, int node)
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{
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unsigned int cpu;
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/* Wrap: we always want a cpu. */
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i %= num_online_cpus();
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cpu = (node == NUMA_NO_NODE) ?
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cpumask_nth(i, cpu_online_mask) :
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sched_numa_find_nth_cpu(cpu_online_mask, i, node);
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WARN_ON(cpu >= nr_cpu_ids);
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return cpu;
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}
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EXPORT_SYMBOL(cpumask_local_spread);
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static DEFINE_PER_CPU(int, distribute_cpu_mask_prev);
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/**
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* Returns an arbitrary cpu within srcp1 & srcp2.
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*
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* Iterated calls using the same srcp1 and srcp2 will be distributed within
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* their intersection.
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*
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* Returns >= nr_cpu_ids if the intersection is empty.
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*/
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unsigned int cpumask_any_and_distribute(const struct cpumask *src1p,
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const struct cpumask *src2p)
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{
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unsigned int next, prev;
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/* NOTE: our first selection will skip 0. */
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prev = __this_cpu_read(distribute_cpu_mask_prev);
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next = find_next_and_bit_wrap(cpumask_bits(src1p), cpumask_bits(src2p),
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nr_cpumask_bits, prev + 1);
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if (next < nr_cpu_ids)
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__this_cpu_write(distribute_cpu_mask_prev, next);
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return next;
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}
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EXPORT_SYMBOL(cpumask_any_and_distribute);
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unsigned int cpumask_any_distribute(const struct cpumask *srcp)
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{
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unsigned int next, prev;
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/* NOTE: our first selection will skip 0. */
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prev = __this_cpu_read(distribute_cpu_mask_prev);
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next = find_next_bit_wrap(cpumask_bits(srcp), nr_cpumask_bits, prev + 1);
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if (next < nr_cpu_ids)
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__this_cpu_write(distribute_cpu_mask_prev, next);
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return next;
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}
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EXPORT_SYMBOL(cpumask_any_distribute);
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