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61 lines
1.4 KiB
61 lines
1.4 KiB
#ifndef __ASM_GENERIC_GETORDER_H |
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#define __ASM_GENERIC_GETORDER_H |
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#ifndef __ASSEMBLY__ |
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#include <linux/compiler.h> |
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#include <linux/log2.h> |
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/* |
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* Runtime evaluation of get_order() |
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*/ |
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static inline __attribute_const__ |
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int __get_order(unsigned long size) |
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{ |
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int order; |
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size--; |
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size >>= PAGE_SHIFT; |
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#if BITS_PER_LONG == 32 |
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order = fls(size); |
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#else |
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order = fls64(size); |
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#endif |
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return order; |
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} |
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/** |
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* get_order - Determine the allocation order of a memory size |
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* @size: The size for which to get the order |
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* |
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* Determine the allocation order of a particular sized block of memory. This |
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* is on a logarithmic scale, where: |
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* |
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* 0 -> 2^0 * PAGE_SIZE and below |
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* 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1 |
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* 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1 |
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* 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1 |
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* 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1 |
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* ... |
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* |
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* The order returned is used to find the smallest allocation granule required |
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* to hold an object of the specified size. |
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* |
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* The result is undefined if the size is 0. |
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* |
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* This function may be used to initialise variables with compile time |
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* evaluations of constants. |
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*/ |
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#define get_order(n) \ |
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( \ |
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__builtin_constant_p(n) ? ( \ |
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((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \ |
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(((n) < (1UL << PAGE_SHIFT)) ? 0 : \ |
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ilog2((n) - 1) - PAGE_SHIFT + 1) \ |
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) : \ |
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__get_order(n) \ |
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) |
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#endif /* __ASSEMBLY__ */ |
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#endif /* __ASM_GENERIC_GETORDER_H */
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