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*参照元 [#o91f5cd0] #backlinks *説明 [#me69d31d] -パス: [[linux-4.4.1/include/asm-generic/getorder.h]] -FIXME: これは何？ --説明 **引数 [#ge65fa8d] -unsigned long n -- **返り値 [#a010eee4] -unsigned long -int -- **参考 [#d62bcd7a] *実装 [#a1e32e86] /** * get_order - Determine the allocation order of a memory size * @size: The size for which to get the order * * Determine the allocation order of a particular sized block of memory. This * is on a logarithmic scale, where: * * 0 -> 2^0 * PAGE_SIZE and below * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1 * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1 * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1 * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1 * ... * * The order returned is used to find the smallest allocation granule required * to hold an object of the specified size. * * The result is undefined if the size is 0. * * This function may be used to initialise variables with compile time * evaluations of constants. */ #define get_order(n) \ ( \ __builtin_constant_p(n) ? ( \ ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \ (((n) < (1UL << PAGE_SHIFT)) ? 0 : \ ilog2((n) - 1) - PAGE_SHIFT + 1) \ ) : \ __get_order(n) \ - --[[linux-4.4.1/ilog2()]] --[[linux-4.4.1/__get_order()]] ) *コメント [#f20c7fed]
