On Wed 05-06-13 11:32:15, Frank Mehnert wrote: [...] > Thank you very much for your help. As I said, this problem happens _only_ > with NUMA_BALANCING enabled. I understand that you treat the VirtualBox > code as untrusted but the reason for the problem is that some assumption > is obviously not met: The VirtualBox code assumes that the memory it > allocates using case A and case B is > > 1. always present and > 2. will always be backed by the same phyiscal memory > > over the entire life time. Enabling NUMA_BALANCING seems to make this > assumption false. I only want to know why. As I said earlier. Both the manual node migration and numa_fault handler do not migrate pages with elevated ref count (your A case) and pages that are not on the LRU. So if your Referenced pages might be on the LRU then you probably have to look into numamigrate_isolate_page and do an exception for PageReserved pages. But I am a bit suspicious this is the cause because the reclaim doesn't consider PageReserved pages either so they could get reclaimed. Or maybe you have handled that path in your kernel. Or the other option is that you depend on a timing or something like that which doesn't hold anymore. That would be hard to debug though. > I see, you don't believe me. I will add more code to the kernel logging > which pages were migrated. Simple test for PageReserved flag in numamigrate_isolate_page should tell you more. This would cover the migration part. Another potential problem could be that the page might get unmapped and marked for the numa fault (see do_numa_page). So maybe your code just assumes that the page even doesn't get unmapped? -- Michal Hocko 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>