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. -- Mel Gorman SUSE Labs -- 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>