On Fri, Aug 08, 2014 at 05:27:15PM +0200, Vlastimil Babka wrote: > On 07/09/2014 10:13 AM, Mel Gorman wrote: > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1604,6 +1604,9 @@ again: > > } > > > > __mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order)); > > This can underflow zero, right? > Yes, because of per-cpu accounting drift. > > + if (zone_page_state(zone, NR_ALLOC_BATCH) == 0 && > > AFAICS, zone_page_state will correct negative values to zero only for > CONFIG_SMP. Won't this check be broken on !CONFIG_SMP? > On !CONFIG_SMP how can there be per-cpu accounting drift that would make that counter negative? -- 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>