On Mon, Apr 7, 2014 at 2:25 PM, Mel Gorman <mgorman@xxxxxxx> wrote: > On Mon, Apr 07, 2014 at 12:42:40PM -0700, H. Peter Anvin wrote: >> On 04/07/2014 12:36 PM, 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? >> > >> > 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). >> > >> >> David Vrabel has a patchset which I presumed would be pulled through the >> Xen tree this merge window: >> >> [PATCHv5 0/8] x86/xen: fixes for mapping high MMIO regions (and remove >> _PAGE_IOMAP) >> >> That frees up this bit. >> > > Thanks, I was not aware of that patch. Based on it, I intend to force > automatic NUMA balancing to depend on !XEN and see what the reaction is. If > support for Xen is really required then it potentially be re-enabled if/when > that series is merged assuming they do not need the bit for something else. > Amazon EC2 does have large memory instance types with NUMA exposed to the guest (e.g. c3.8xlarge, i2.8xlarge, etc), so it'd be preferable (to me anyway) if we didn't require !XEN. -- 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>