On Wed, Nov 17, 2010 at 04:22:47PM +0000, Mel Gorman wrote: > @@ -485,8 +500,8 @@ static unsigned long compact_zone_order(struct zone *zone, > .nr_migratepages = 0, > .order = order, > .migratetype = allocflags_to_migratetype(gfp_mask), > + .migrate_fast_scan = true, > .zone = zone, > - .sync = false, > }; > INIT_LIST_HEAD(&cc.freepages); > INIT_LIST_HEAD(&cc.migratepages); > @@ -502,8 +517,8 @@ unsigned long reclaimcompact_zone_order(struct zone *zone, > .nr_migratepages = 0, > .order = order, > .migratetype = allocflags_to_migratetype(gfp_mask), > + .migrate_fast_scan = false, > .zone = zone, > - .sync = true, > }; Same as for the previous feature (sync/async migrate) I'd prefer if this was a __GFP_ flag (khugepaged will do the no-fast-scan version, page fault will only run compaction in fast scan mode) and if we removed the reclaimcompact_zone_order and we stick with the interleaving of shrinker and try_to_compact_pages from the alloc_pages caller, with no nesting of compaction inside the shrinker. Another possibility would be to not have those as __GFP flags, and to always do the first try_to_compact_pages with async+fast_scan, then call the shrinker and then all next try_to_compact_pages would be called with sync+no_fast_scan mode. But I love if we can further decrease the risk of too long page hugepage page fault before the normal page fallback, and to have a __GFP_ flag for these two. Even the same __GFP flag could work for both... So my preference would be to nuke reclaimcompact_zone_order, only stick to compact_zone_order and the current interleaving, and add a __GFP_COMPACT_FAST used by the hugepmd page fault (that will enable both async migrate and fast-scan). khugepaged and hugetlbfs won't use __GFP_COMPACT_FAST. I'm undecided if a __GFP_ flag is needed to differentiate the callers, or if we should just run the first try_to_compact_pages in "optimistic" mode by default. -- 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>