On Thu, Oct 04, 2012 at 01:50:57AM +0200, Andrea Arcangeli wrote: > This is where the dynamically allocated task_autonuma structure is > being handled. > > This is the structure holding the per-thread NUMA statistics generated > by the NUMA hinting page faults. This per-thread NUMA statistical > information is needed by sched_autonuma_balance to make optimal NUMA > balancing decisions. > > It also contains the task_selected_nid which hints the stock CPU > scheduler on the best NUMA node to schedule this thread on (as decided > by sched_autonuma_balance). > > The reason for keeping this outside of the task_struct besides not > using too much kernel stack, is to only allocate it on NUMA > hardware. So the non NUMA hardware only pays the memory of a pointer > in the kernel stack (which remains NULL at all times in that case). > > If the kernel is compiled with CONFIG_AUTONUMA=n, not even the pointer > is allocated on the kernel stack of course. > > Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> There is a possibility that someone will complain about the extra kmalloc() during fork that is now necessary for the autonuma structure. Microbenchmarks will howl but who cares -- autonuma only makes sense for long-lived processes anyway. It may be necessary in the future to defer this allocation until the process has consumed a few CPU seconds and likely to hang around for a while. Overkill for now though so Acked-by: Mel Gorman <mgorman@xxxxxxx> -- 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>