On Thu, Jan 31, 2013 at 4:30 PM, Gleb Natapov <g...@redhat.com> wrote: >> > >> > Avi/Michael do you remember why mincore can't be used to check if a guest >> page is unmapped? >> >> A page may be not in core, but also nonzero (for example swap). > Yes, mincore() should not be used as zero page check, but it can be used > as an indicator that page can be dealt with in dead stage of migration > since it is likely zero and will not take much time to send.
Or it's swapped, in which case we know nothing about it. > It is > possible to call madvise(MADV_WILLNEED) on them meanwhile to pre-load > swap without faulting on each page individually. During migration you're faulting like mad anyway.
