On Tue, May 29, 2012 at 03:16:25PM +0200, Peter Zijlstra wrote: > 24 bytes per page.. or ~0.6% of memory gone. This is far too great a > price to pay. I don't think it's too great, memcg uses for half of that and yet nobody is booting with cgroup_disable=memory even on not-NUMA servers with less RAM. > At LSF/MM Rik already suggested you limit the number of pages that can > be migrated concurrently and use this to move the extra list_head out of > struct page and into a smaller amount of extra structures, reducing the > total overhead. It would reduce the memory overhead but it'll make the code more complex and it'll require more locking, plus allowing for very long migration lrus, provides an additional means of false-sharing avoidance. Those are lrus, if the last_nid false sharing logic will pass, the page still has to reach the tail of the list before being migrated, if false sharing happens in the meanwhile we'll remove it from the lru. But I'm all for experimenting. It's just not something I had the time to try yet. I will certainly love to see how it performs by reducing the max size of the list. I totally agree it's a good idea to try it out, and I don't exclude it will work fine, but it's not obvious it's worth the memory saving. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>