Hi Hannes, On Wed, Jan 09, 2013 at 01:56:12AM -0500, Johannes Weiner wrote: > On Wed, Jan 09, 2013 at 03:21:13PM +0900, Minchan Kim wrote: > > Recently, Luigi reported there are lots of free swap space when > > OOM happens. It's easily reproduced on zram-over-swap, where > > many instance of memory hogs are running and laptop_mode is enabled. > > > > Luigi reported there was no problem when he disabled laptop_mode. > > The problem when I investigate problem is following as. > > > > try_to_free_pages disable may_writepage if laptop_mode is enabled. > > shrink_page_list adds lots of anon pages in swap cache by > > add_to_swap, which makes pages Dirty and rotate them to head of > > inactive LRU without pageout. If it is repeated, inactive anon LRU > > is full of Dirty and SwapCache pages. > > > > In case of that, isolate_lru_pages fails because it try to isolate > > clean page due to may_writepage == 0. > > > > The may_writepage could be 1 only if total_scanned is higher than > > writeback_threshold in do_try_to_free_pages but unfortunately, > > VM can't isolate anon pages from inactive anon lru list by > > above reason and we already reclaimed all file-backed pages. > > So it ends up OOM killing. > > > > This patch prevents to add a page to swap cache unnecessary when > > may_writepage is unset so anoymous lru list isn't full of > > Dirty/Swapcache page. So VM can isolate pages from anon lru list, > > which ends up setting may_writepage to 1 and could swap out > > anon lru pages. When OOM triggers, I confirmed swap space was full. > > > > Reported-by: Luigi Semenzato <semenzato@xxxxxxxxxx> > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > We used to ignore the page's writeback state on isolation in the past, > could you include a reference to since when this problem has been in Good idea. It has existed since f80c067[mm: zone_reclaim: make isolate_lru_page() filter-aware] I will write down it in changelog. > the tree? Also, would it make sense to tag it for one of the stable > trees? If Luigi confirmed it, I will Cc stable@xxxxxxxxxxxxxxx in next spin. Thanks! > > -- > 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> -- 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>