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
)
40 for_each_possible_cpu(cpu
)
41 memset((void *)pcpu_chunk_addr(chunk
, cpu
, 0) + off
, 0, size
);
46 static void pcpu_depopulate_chunk(struct pcpu_chunk
*chunk
, int off
, int size
)
51 static struct pcpu_chunk
*pcpu_create_chunk(void)
53 const int nr_pages
= pcpu_group_sizes
[0] >> PAGE_SHIFT
;
54 struct pcpu_chunk
*chunk
;
58 chunk
= pcpu_alloc_chunk();
62 pages
= alloc_pages(GFP_KERNEL
, order_base_2(nr_pages
));
64 pcpu_free_chunk(chunk
);
68 for (i
= 0; i
< nr_pages
; i
++)
69 pcpu_set_page_chunk(nth_page(pages
, i
), chunk
);
72 chunk
->base_addr
= page_address(pages
) - pcpu_group_offsets
[0];
76 static void pcpu_destroy_chunk(struct pcpu_chunk
*chunk
)
78 const int nr_pages
= pcpu_group_sizes
[0] >> PAGE_SHIFT
;
80 if (chunk
&& chunk
->data
)
81 __free_pages(chunk
->data
, order_base_2(nr_pages
));
82 pcpu_free_chunk(chunk
);
85 static struct page
*pcpu_addr_to_page(void *addr
)
87 return virt_to_page(addr
);
90 static int __init
pcpu_verify_alloc_info(const struct pcpu_alloc_info
*ai
)
92 size_t nr_pages
, alloc_pages
;
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");
100 nr_pages
= (ai
->groups
[0].nr_units
* ai
->unit_size
) >> PAGE_SHIFT
;
101 alloc_pages
= roundup_pow_of_two(nr_pages
);
103 if (alloc_pages
> nr_pages
)
104 printk(KERN_WARNING
"percpu: wasting %zu pages per chunk\n",
105 alloc_pages
- nr_pages
);
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