On 04/01/2014 11:03 PM, Cyrill Gorcunov wrote: > On Tue, Apr 01, 2014 at 11:43:11AM -0700, Linus Torvalds wrote: >> On Tue, Apr 1, 2014 at 11:18 AM, David Vrabel <david.vrabel@xxxxxxxxxx> wrote: >>> >>> I don't think it's sufficient to avoid collisions with bits used only >>> with P=0. The original value of this bit must be retained when the >>> _PAGE_NUMA bit is set/cleared. >>> >>> Bit 7 is PAT[2] and whilst Linux currently sets up the PAT such that >>> PAT[2] is a 'don't care', there has been talk up adjusting the PAT to >>> include more types. So I'm not sure it's a good idea to use bit 7. >>> >>> What's wrong with using e.g., bit 62? And not supporting this NUMA >>> rebalancing feature on 32-bit non-PAE builds? >> >> Sounds good to me, but it's not available in 32-bit PAE. The high bits >> are all reserved, afaik. >> >> But you'd have to be insane to care about NUMA balancing on 32-bit, >> even with PAE. So restricting it to x86-64 and using the high bits (I >> think bits 52-62 are all available to SW) sounds fine to me. >> >> Same goes for soft-dirty. I think it's fine if we say that you won't >> have soft-dirty with a 32-bit kernel. Even with PAE. > > Well, at the moment we use soft-dirty for x86-64 only in criu but there > were plans to implement complete 32bit support as well. While personally > I don't mind dropping soft-dirty for non x86-64 case, I would like > to hear Pavel's opinion, Pavel? We (Parallels) don't have plans on C/R on 32-bit kernels, but I speak only for Parallels. However, people I know who need 32-bit C/R use ARM :) > (n.b, i'm still working on cleaning up _page bits, it appeared to > be harder than I've been expecting). > . Thanks, Pavel -- 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>