If hugetlb pages are requested in mmap or shmget system calls, a huge page size other than default can be requested. This is accomplished by encoding the log2 of the huge page size in the upper bits of the flag argument. asm-generic and arch specific headers all define the same values for these encodings. Put common definitions in a single header file. arch specific code can still override if desired. Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> --- include/uapi/asm-generic/hugetlb_encode.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 include/uapi/asm-generic/hugetlb_encode.h diff --git a/include/uapi/asm-generic/hugetlb_encode.h b/include/uapi/asm-generic/hugetlb_encode.h new file mode 100644 index 0000000..aa09fc0 --- /dev/null +++ b/include/uapi/asm-generic/hugetlb_encode.h @@ -0,0 +1,30 @@ +#ifndef _ASM_GENERIC_HUGETLB_ENCODE_H_ +#define _ASM_GENERIC_HUGETLB_ENCODE_H_ + +/* + * Several system calls take a flag to request "hugetlb" huge pages. + * Without further specification, these system calls will use the + * system's default huge page size. If a system supports multiple + * huge page sizes, the desired huge page size can be specified in + * bits [26:31] of the flag arguments. The value in these 6 bits + * will encode the log2 of the huge page size. + * + * The following definitions are associated with this huge page size + * encoding in flag arguments. System call specific header files + * that use this encoding should include this file. They can then + * provide definitions based on these with their own specific prefix. + * for example #define MAP_HUGE_SHIFT HUGETLB_FLAG_ENCODE_SHIFT. + */ + +#define HUGETLB_FLAG_ENCODE_SHIFT 26 +#define HUGETLB_FLAG_ENCODE_MASK 0x3f + +#define HUGETLB_FLAG_ENCODE_512KB (19 << MAP_HUGE_SHIFT +#define HUGETLB_FLAG_ENCODE_1MB (20 << MAP_HUGE_SHIFT) +#define HUGETLB_FLAG_ENCODE_2MB (21 << MAP_HUGE_SHIFT) +#define HUGETLB_FLAG_ENCODE_8MB (23 << MAP_HUGE_SHIFT) +#define HUGETLB_FLAG_ENCODE_16MB (24 << MAP_HUGE_SHIFT) +#define HUGETLB_FLAG_ENCODE_1GB (30 << MAP_HUGE_SHIFT) +#define HUGETLB_FLAG_ENCODE__16GB (34 << MAP_HUGE_SHIFT) + +#endif /* _ASM_GENERIC_HUGETLB_ENCODE_H_ */ -- 2.7.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
