On Thu, Oct 04, 2012 at 01:50:46AM +0200, Andrea Arcangeli wrote: > The objective of _PAGE_NUMA is to be able to trigger NUMA hinting page > faults to identify the per NUMA node working set of the thread at > runtime. > > Arming the NUMA hinting page fault mechanism works similarly to > setting up a mprotect(PROT_NONE) virtual range: the present bit is > cleared at the same time that _PAGE_NUMA is set, so when the fault > triggers we can identify it as a NUMA hinting page fault. > That implies that there is an atomic update requirement or at least an ordering requirement -- present bit must be cleared before setting NUMA bit. No doubt it'll be clear later in the series how this is accomplished. What you propose seems ok but it all depends how it's implemented so I'm leaving my ack off this particular patch for now. -- 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>