On Thu 10-08-17 10:21:18, Michal Hocko wrote: > On Tue 08-08-17 19:48:55, Andrea Arcangeli wrote: > [...] > > The bug corrected by this patch 1/2 I pointed it out last week while > > reviewing other oom reaper fixes so that looks fine. > > > > However I'd prefer to dump MMF_UNSTABLE for good instead of adding > > more of it. It can be replaced with unmap_page_range in > > __oom_reap_task_mm with a function that arms a special migration entry > > so that no branchs are added to the fast paths and it's all hidden > > inside is_migration_entry slow paths. > > This sounds like an interesting idea but I would like to address the > _correctness_ issue first and optimize on top of it. If for nothing else > backporting a follow up fix sounds easier than a complete rework. There > are quite some callers of is_migration_entry and the patch won't be > trivial either. So can we focus on the fix first please? Btw, if the overhead is a concern then we can add a jump label and only make the code active only while the OOM is in progress. We already do count all oom victims so we have a clear entry and exit points. This would still sound easier to do than teach every is_migration_entry a new migration entry type and handle it properly, not to mention make everybody aware of this for future callers of is_migration_entry. -- Michal Hocko SUSE Labs -- 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>
