On Mon, 10 Sep 2012 09:18:30 +0800 Shaohua Li <shli@xxxxxxxxxx> wrote: > isolate_migratepages_range() might isolate none pages, for example, when > zone->lru_lock is contended and compaction is async. In this case, we should > abort compaction, otherwise, compact_zone will run a useless loop and make > zone->lru_lock is even contended. > > ... > > @@ -838,12 +838,14 @@ static unsigned long compact_zone_order( > .migratetype = allocflags_to_migratetype(gfp_mask), > .zone = zone, > .sync = sync, > - .contended = contended, > }; > INIT_LIST_HEAD(&cc.freepages); > INIT_LIST_HEAD(&cc.migratepages); > > - return compact_zone(zone, &cc); > + ret = compact_zone(zone, &cc); > + if (contended) > + *contended = cc.contended; > + return ret; > } > >From a quick read, `contended' is never NULL here. And defining the interface so that `contended' must be a valid pointer is a good change, IMO - it results in simpler and faster code. Alas, try_to_compact_pages()'s kerneldoc altogether forgets to describe this argument. Mel's mm-compaction-capture-a-suitable-high-order-page-immediately-when-it-is-made-available.patch adds a `pages' arg and forgets to document that as well. -- 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>