On Mon, 22 Jul 2013, Lisa Du wrote: > 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. Can you verify that by doing a cat /proc/buddyinfo ? > 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; > } Mel? -- 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>