On Tue 10-05-16 16:07:14, Joonsoo Kim wrote: > 2016-05-05 4:40 GMT+09:00 Michal Hocko <mhocko@xxxxxxxxxx>: > > On Thu 05-05-16 00:30:35, Joonsoo Kim wrote: > >> 2016-05-04 18:21 GMT+09:00 Michal Hocko <mhocko@xxxxxxxxxx>: > > [...] > >> > Do we really consume 512B of stack during reclaim. That sounds more than > >> > worrying to me. > >> > >> Hmm...I checked it by ./script/stackusage and result is as below. > >> > >> shrink_zone() 128 > >> shrink_zone_memcg() 248 > >> shrink_active_list() 176 > >> > >> We have a call path that shrink_zone() -> shrink_zone_memcg() -> > >> shrink_active_list(). > >> I'm not sure whether it is the deepest path or not. > > > > This is definitely not the deepest path. Slab shrinkers can take more > > but 512B is still a lot. Some call paths are already too deep when > > calling into the allocator and some of them already use GFP_NOFS to > > prevent from potentially deep callchain slab shrinkers. Anyway worth > > exploring for better solutions. > > > > And I believe it would be better to solve this in the stackdepot > > directly so other users do not have to invent their own ways around the > > same issue. I have just checked the code and set_track uses save_stack > > which does the same thing and it seems to be called from the slab > > allocator. I have missed this usage before so the problem already does > > exist. It would be unfair to request you to fix that in order to add a > > new user. It would be great if this got addressed though. > > Yes, fixing it in stackdepot looks more reasonable. > Then, I will just change PAGE_OWNER_STACK_DEPTH from 64 to 16 and > leave the code as is for now. With this change, we will just consume 128B stack > and would not cause stack problem. If anyone has an objection, > please let me know. 128B is still quite a lot but considering there is a plan to make it more robust I can live with it as a temporary workaround. -- 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>