On 05/24, Michal Hocko wrote: > > On Mon 23-05-16 17:14:19, Oleg Nesterov wrote: > > On 05/23, Michal Hocko wrote: > [...] > > > Could you add some tracing and see what are the numbers > > > above? > > > > with the patch below I can press Ctrl-C when it hangs, this breaks the > > endless loop and the output looks like > > > > vmscan: ZONE=ffffffff8189f180 0 scanned=0 pages=6 > > vmscan: ZONE=ffffffff8189eb00 0 scanned=1 pages=0 > > ... > > vmscan: ZONE=ffffffff8189eb00 0 scanned=2 pages=1 > > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > > ... > > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > > vmscan: ZONE=ffffffff8189f180 0 scanned=4 pages=6 > > > > the numbers are always small. > > Small but scanned is not 0 and constant which means it either gets reset > repeatedly (something gets freed) or we have stopped scanning. Which > pattern can you see? I assume that the swap space is full at the time > (could you add get_nr_swap_pages() to the output). no, I tested this without SWAP, > Also zone->name would > be better than the pointer. Yes, forgot to mention, this is DMA32. To remind, only 512m of RAM so this is natural. > I am trying to reproduce but your test case always hits the oom killer: Did you try to run it in a loop? Usually it takes a while before the system hangs. > Swap: 138236 57740 80496 perhaps this makes a difference? See above, I have no SWAP. So. I spent almost the whole day trying to understand whats going on, and of course I failed. But. It _seems to me_ that the kernel "leaks" some pages in LRU_INACTIVE_FILE list because inactive_file_is_low() returns the wrong value. And do not even ask me why I think so, unlikely I will be able to explain ;) to remind, I never tried to read vmscan.c before. But. if I change lruvec_lru_size() - return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru); + return zone_page_state_snapshot(lruvec_zone(lruvec), NR_LRU_BASE + lru); the problem goes away too. To remind, it also goes away if I change calculate_normal_threshold() to return zero, and it was not clear why. Now we can probably conclude that that this is because the change obviouslt affects lruvec_lru_size(). Oleg. -- 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>