Hello, On Mon, Jul 22, 2013 at 09:58:17PM -0700, Lisa Du wrote: > Dear Sir: > Currently I met a possible deadloop in direct reclaim. After run plenty of the application, system run into a status that system memory is very fragmentized. Like only order-0 and order-1 memory left. > Then one process required a order-2 buffer but it enter an endless direct reclaim. From my trace log, I can see this loop already over 200,000 times. Kswapd was first wake up and then go back to sleep as it cannot rebalance this order's memory. But zone->all_unreclaimable remains 1. > Though direct_reclaim every time returns no pages, but as zone->all_unreclaimable = 1, so it loop again and again. Even when zone->pages_scanned also becomes very large. It will block the process for long time, until some watchdog thread detect this and kill this process. Though it's in __alloc_pages_slowpath, but it's too slow right? Maybe cost over 50 seconds or even more. > I think it's not as expected right? Can we also add below check in the function all_unreclaimable() to terminate this loop? > > @@ -2355,6 +2355,8 @@ static bool all_unreclaimable(struct zonelist *zonelist, > continue; > if (!zone->all_unreclaimable) > return false; > + if (sc->nr_reclaimed == 0 && !zone_reclaimable(zone)) > + return true; > } > BTW: I'm using kernel3.4, I also try to search in the kernel3.9, didn't see a possible fix for such issue. Or is anyone also met such issue before? Any comment will be welcomed, looking forward to your reply! > > Thanks! I'd like to ask somethigs. 1. Do you have enabled swap? 2. Do you enable CONFIG_COMPACTION? 3. Could we get your zoneinfo via cat /proc/zoneinfo? 4. If you disabled watchdog thread, you could see OOM sometime although it takes very long time? > > Best Regards > Lisa Du > -- Kind regards, Minchan Kim -- 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>