On 06/15/2012 01:10 AM, KOSAKI Motohiro wrote: > On Thu, Jun 14, 2012 at 10:57 AM, Minchan Kim <minchan@xxxxxxxxxx> wrote: >> Hi KOSAKI, >> >> Sorry for late response. >> Let me ask a question about description. >> >> On Thu, Jun 14, 2012 at 04:13:12AM -0400, kosaki.motohiro@xxxxxxxxx wrote: >>> From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> >>> >>> Currently, do_try_to_free_pages() can enter livelock. Because of, >>> now vmscan has two conflicted policies. >>> >>> 1) kswapd sleep when it couldn't reclaim any page when reaching >>> priority 0. This is because to avoid kswapd() infinite >>> loop. That said, kswapd assume direct reclaim makes enough >>> free pages to use either regular page reclaim or oom-killer. >>> This logic makes kswapd -> direct-reclaim dependency. >>> 2) direct reclaim continue to reclaim without oom-killer until >>> kswapd turn on zone->all_unreclaimble. This is because >>> to avoid too early oom-kill. >>> This logic makes direct-reclaim -> kswapd dependency. >>> >>> In worst case, direct-reclaim may continue to page reclaim forever >>> when kswapd sleeps forever. >> >> I have tried imagined scenario you mentioned above with code level but >> unfortunately I got failed. >> If kswapd can't meet high watermark on order-0, it doesn't sleep if I don't miss something. > > pgdat_balanced() doesn't recognized zone. Therefore kswapd may sleep > if node has multiple zones. Hm ok, I realized my descriptions was > slightly misleading. priority 0 is not needed. bakance_pddat() calls > pgdat_balanced() > every priority. Most easy case is, movable zone has a lot of free pages and > normal zone has no reclaimable page. > > btw, current pgdat_balanced() logic seems not correct. kswapd should > sleep only if every zones have much free pages than high water mark > _and_ 25% of present pages in node are free. > Sorry. I can't understand your point. Current kswapd doesn't sleep if relevant zones don't have free pages above high watermark. It seems I am missing your point. Please anybody correct me. -- 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>