On 04/14/2016 07:24 PM, Vlastimil Babka wrote: >> > @@ -1459,8 +1459,8 @@ static enum compact_result compact_zone( >> > zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; >> > } >> > >> > - if (cc->migrate_pfn == start_pfn) >> > - cc->whole_zone = true; >> > + cc->whole_zone = cc->migrate_pfn == start_pfn && >> > + cc->free_pfn == pageblock_start_pfn(end_pfn - 1); >> > >> > cc->last_migrated_pfn = 0; > This would be for Michal, but I agree.
So there's an alternative here that wouldn't have the danger of missing cc->whole_zone multiple time due to races. When resetting either one scanner to zone boundary, reset the other as well (and set cc->whole_zone). I think the situations, where not doing that have any (performance) advantage, are rare.
