1 /* 2 * mm/percpu-km.c - kernel memory based chunk allocation 3 * 4 * Copyright (C) 2010 SUSE Linux Products GmbH 5 * Copyright (C) 2010 Tejun Heo <tj@kernel.org> 6 * 7 * This file is released under the GPLv2. 8 * 9 * Chunks are allocated as a contiguous kernel memory using gfp 10 * allocation. This is to be used on nommu architectures. 11 * 12 * To use percpu-km, 13 * 14 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig. 15 * 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 18 * fine. 19 * 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. 23 * 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. 28 */ 29 30 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) 31 #error "contiguous percpu allocation is incompatible with paged first chunk" 32 #endif 33 34 #include <linux/log2.h> 35 36 static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size) 37 { 38 unsigned int cpu; 39 40 for_each_possible_cpu(cpu) 41 memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size); 42 43 return 0; 44 } 45 46 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size) 47 { 48 /* nada */ 49 } 50 51 static struct pcpu_chunk *pcpu_create_chunk(void) 52 { 53 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 54 struct pcpu_chunk *chunk; 55 struct page *pages; 56 int i; 57 58 chunk = pcpu_alloc_chunk(); 59 if (!chunk) 60 return NULL; 61 62 pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages)); 63 if (!pages) { 64 pcpu_free_chunk(chunk); 65 return NULL; 66 } 67 68 for (i = 0; i < nr_pages; i++) 69 pcpu_set_page_chunk(nth_page(pages, i), chunk); 70 71 chunk->data = pages; 72 chunk->base_addr = page_address(pages) - pcpu_group_offsets[0]; 73 return chunk; 74 } 75 76 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) 77 { 78 const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; 79 80 if (chunk && chunk->data) 81 __free_pages(chunk->data, order_base_2(nr_pages)); 82 pcpu_free_chunk(chunk); 83 } 84 85 static struct page *pcpu_addr_to_page(void *addr) 86 { 87 return virt_to_page(addr); 88 } 89 90 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) 91 { 92 size_t nr_pages, alloc_pages; 93 94 /* all units must be in a single group */ 95 if (ai->nr_groups != 1) { 96 printk(KERN_CRIT "percpu: can't handle more than one groups\n"); 97 return -EINVAL; 98 } 99 100 nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; 101 alloc_pages = roundup_pow_of_two(nr_pages); 102 103 if (alloc_pages > nr_pages) 104 printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n", 105 alloc_pages - nr_pages); 106 107 return 0; 108 } 109