On 06/12/2012 07:13 PM, Andi Kleen wrote:
From: Andi Kleen<ak@xxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
There was some desire in large applications using MAP_HUGETLB/SHM_HUGETLB to use 1GB huge pages on some mappings, and stay with 2MB on others. This is useful together with NUMA policy: use 2MB interleaving on some mappings, but 1GB on local mappings. This patch extends the IPC/SHM syscall interfaces slightly to allow specifying the page size.
This would also be useful for emulators such as qemu-kvm, which want the guest memory to be 2MB aligned. That would require extending mmap to specify the desired alignment, which may be possible using the upper bits of the mmap flags, like you did for the shm interface.
+#define MAP_HUGE_2MB (21<< MAP_HUGE_SHIFT) +#define MAP_HUGE_1GB (30<< MAP_HUGE_SHIFT)
Nice idea, that way each architecture can define the names for possible offsets, yet the numeric values will always line up between all of them.
+ * Assume these are all power of twos. + * When 0 use the default page size. + */ +#define SHM_HUGE_SHIFT 26 +#define SHM_HUGE_MASK 0x3f +#define SHM_HUGE_2MB (21<< SHM_HUGE_SHIFT) +#define SHM_HUGE_1GB (30<< SHM_HUGE_SHIFT) + +#ifdef __KERNEL__
Excellent, this is very similar to what I was thinking about implementing myself, in order to pass "desired alignment" information to my implementation of arch_get_unmapped_area(_topdown) :) -- 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>