On Tue, 22 Nov 2011 22:25:46 -0800 (pst), David Rientjes wrote: > On Wed, 23 Nov 2011, Miao Xie wrote: > >> This is a good idea. But I worry that oom will happen easily, because we do >> direct reclamation and compact by mems_allowed. >> > > Memory compaction actually iterates through each zone regardless of > whether it's allowed or not in the current context. Recall that the > nodemask passed into __alloc_pages_nodemask() is non-NULL only when there > is a mempolicy that restricts the allocations by MPOL_BIND. That nodemask > is not protected by get_mems_allowed(), so there's no change in > compaction's behavior with my patch. That nodemask is also protected by get_mems_allowed(). > Direct reclaim does, however, require mems_allowed staying constant > without the risk of early oom as you mentioned. It has its own > get_mems_allowed(), though, so it doesn't have the opportunity to change > until returning to the page allocator. It's possible that mems_allowed > will be different on the next call to get_pages_from_freelist() but we > don't know anything about that context: it's entirely possible that the > set of new mems has an abundance of free memory or are completely depleted > as well. So there's no strict need for consistency between the set of > allowed nodes during reclaim and the subsequent allocation attempt. All > we care about is that reclaim has a consistent set of allowed nodes to > determine whether it's making progress or not. > Agree. -- 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>