On 07/04/14 20:36, Cyrill Gorcunov wrote: > On Mon, Apr 07, 2014 at 12:27:10PM -0700, H. Peter Anvin wrote: >> On 04/07/2014 11:28 AM, Mel Gorman wrote: >>> >>> I had considered the soft-dirty tracking usage of the same bit. I thought I'd >>> be able to swizzle around it or a further worst case of having soft-dirty and >>> automatic NUMA balancing mutually exclusive. Unfortunately upon examination >>> it's not obvious how to have both of them share a bit and I suspect any >>> attempt to will break CRIU. In my current tree, NUMA_BALANCING cannot be >>> set if MEM_SOFT_DIRTY which is not particularly satisfactory. Next on the >>> list is examining if _PAGE_BIT_IOMAP can be used. >> >> Didn't we smoke the last user of _PAGE_BIT_IOMAP? Not yet. A last minute regression with mapping of I/O regions from userspace was found so I had to drop the series from 3.15. It should be back for 3.16. > Seems so, at least for non-kernel pages (not considering this bit references in > xen code, which i simply don't know but i guess it's used for kernel pages only). Xen uses it for all I/O mappings, both kernel and for userspace. David -- 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>