On Wed, Nov 17, 2010 at 04:22:45PM +0000, Mel Gorman wrote: > @@ -484,6 +486,7 @@ static unsigned long compact_zone_order(struct zone *zone, > .order = order, > .migratetype = allocflags_to_migratetype(gfp_mask), > .zone = zone, > + .sync = false, > }; > INIT_LIST_HEAD(&cc.freepages); > INIT_LIST_HEAD(&cc.migratepages); I like this because I'm very afraid to avoid wait-I/O latencies introduced into hugepage allocations that I prefer to fail quickly and be handled later by khugepaged ;). But I could have khugepaged call this with sync=true... so I'd need a __GFP_ flag that only khugepaged would use to notify compaction should be synchronous for khugepaged (not for the regular allocations in page faults). Can we do this through gfp_mask only? > @@ -500,6 +503,7 @@ unsigned long reclaimcompact_zone_order(struct zone *zone, > .order = order, > .migratetype = allocflags_to_migratetype(gfp_mask), > .zone = zone, > + .sync = true, > }; > INIT_LIST_HEAD(&cc.freepages); > INIT_LIST_HEAD(&cc.migratepages); Is this intentional? That inner compaction invocation is equivalent to the one one interleaved with the shrinker tried before invoking the shrinker. So I don't see why they should differ (one sync and one async). Anyway I'd prefer the inner invocation to be removed as a whole and to keep only going with the interleaving and to keep the two jobs of compaction and shrinking memory fully separated and to stick to the interleaving. If this reclaimcompact_zone_order helps maybe it means compact_zone_order isn't doing the right thing and we're hiding it by randomly calling it more frequently... I can see a point however in doing: compaction async shrink (may wait) (scan 500 pages, freed 32 pages) compaction sync (may wait) to: compaction async shrink (scan 32 pages, freed 0 pages) compaction sync (hugepage generated nobody noticed) shrink (scan 32 pages, freed 0 pages) compaction sync shrink (scan 32 pages, freed 0 pages) [..] -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>