On Fri, Mar 19, 2010 at 03:21:41PM +0900, KOSAKI Motohiro wrote: > > > then, this logic depend on SLAB_DESTROY_BY_RCU, not refcount. > > > So, I think we don't need your [1/11] patch. > > > > > > Am I missing something? > > > > > > > The refcount is still needed. The anon_vma might be valid, but the > > refcount is what ensures that the anon_vma is not freed and reused. > > please please why do we need both mechanism. now cristoph is very busy and I am > de fact reviewer of page migration and mempolicy code. I really hope to understand > your patch. > As in, why not drop the RCU protection of anon_vma altogeter? Mainly, because I think it would be reaching too far for this patchset and it should be done as a follow-up. Putting the ref-count everywhere will change the cache-behaviour of anon_vma more than I'd like to slip into a patchset like this. Secondly, Christoph mentions that SLAB_DESTROY_BY_RCU is used to keep anon_vma cache-hot. For these reasons, removing RCU from these paths and adding the refcount in others is a patch that should stand on its own. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>