Hello, On Mon, Aug 12, 2013 at 08:14:04AM -0700, H. Peter Anvin wrote: > It gets really messy if it is advisory. Suddenly you have the user > thinking they can hotswap a memory bank and they just can't. I'm very skeptical that not doing the strict re-ordering would increase the chance of reaching memory allocation where hot unplug would be impossible by much. Given that, it'd be much better to be able to boot w/o hotunplug capability than to fail boot. The kernel can whine loudly when hotunplug conditions aren't met but I think that really is as far as that should go. > Overall, I'm getting convinced that this whole approach is just doomed > to failure -- it will not provide the user what they expect and what > they need, which is to be able to hotswap any particular chunk of > memory. This means that there has to be a remapping layer, either using > the TLBs (perhaps leveraging the Xen machine page number) or using > things like QPI memory routing. For hot unplug to work in completely generic manner, yeah, there probably needs to be an extra layer of indirection. Have no idea what the correct way to achieve that would be tho. I'm also not sure how practicial memory hot unplug is for physical machines and improving ballooning could be a better approach for vms. Thanks. -- tejun -- 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>