Hello Michal, CC'ed Hugh, On Fri, Jun 03, 2016 at 04:46:00PM +0200, Michal Hocko wrote: > What do you think about the external dependencies mentioned above. Do > you think this is a sufficient argument wrt. occasional higher > latencies? It's a tradeoff and both latencies would be short and uncommon so it's hard to tell. There's also mmput_async for paths that may care about mmput latencies. Exit itself cannot use it, it's mostly for people taking the mm_users pin that may not want to wait for mmput to run. It also shouldn't happen that often, it's a slow path. The whole model inherited from KSM is to deliberately depend only on the mmap_sem + test_exit + mm_count, and never on mm_users, which to me in principle doesn't sound bad. I consider KSM version a "finegrined" implementation but I never thought it would be a problem to wait a bit in exit() in case the slow path hits. I thought it was more of a problem if exit() runs, the parent then start a new task but the memory wasn't freed yet. So I would suggest Hugh to share his view on the down_write/up_write that may temporarily block mmput (until the next test_exit bailout point) vs higher latency in reaching exit_mmap for a real exit(2) that would happen with the proposed change. Thanks! Andrea -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
