2 * mm/percpu-km.c - kernel memory based chunk allocation
4 * Copyright (C) 2010 SUSE Linux Products GmbH
5 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
7 * This file is released under the GPLv2.
9 * Chunks are allocated as a contiguous kernel memory using gfp
10 * allocation. This is to be used on nommu architectures.
14 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
16 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined. It's
17 * not compatible with PER_CPU_KM. EMBED_FIRST_CHUNK should work
20 * - NUMA is not supported. When setting up the first chunk,
21 * @cpu_distance_fn should be NULL or report all CPUs to be nearer
22 * than or at LOCAL_DISTANCE.
24 * - It's best if the chunk size is power of two multiple of
25 * PAGE_SIZE. Because each chunk is allocated as a contiguous
26 * kernel memory block using alloc_pages(), memory will be wasted if
27 * chunk size is not aligned. percpu-km code will whine about it.
30 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
31 #error "contiguous percpu allocation is incompatible with paged first chunk"
34 #include <linux/log2.h>
36 static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
41 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
46 static struct pcpu_chunk *pcpu_create_chunk(void)
48 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
49 struct pcpu_chunk *chunk;
53 chunk = pcpu_alloc_chunk();
57 pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages));
59 pcpu_free_chunk(chunk);
63 for (i = 0; i < nr_pages; i++)
64 pcpu_set_page_chunk(nth_page(pages, i), chunk);
67 chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];
71 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
73 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
75 if (chunk && chunk->data)
76 __free_pages(chunk->data, order_base_2(nr_pages));
77 pcpu_free_chunk(chunk);
80 static struct page *pcpu_addr_to_page(void *addr)
82 return virt_to_page(addr);
85 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
87 size_t nr_pages, alloc_pages;
89 /* all units must be in a single group */
90 if (ai->nr_groups != 1) {
91 printk(KERN_CRIT "percpu: can't handle more than one groups\n");
95 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
96 alloc_pages = roundup_pow_of_two(nr_pages);
98 if (alloc_pages > nr_pages)
99 printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n",
100 alloc_pages - nr_pages);