On Mon, Jan 21, 2013 at 09:39:06AM -0500, Rik van Riel wrote: > On 01/20/2013 08:52 PM, Minchan Kim wrote: > > > From 94086dc7152359d052802c55c82ef19509fe8cce Mon Sep 17 00:00:00 2001 > >From: Minchan Kim <minchan@xxxxxxxxxx> > >Date: Mon, 21 Jan 2013 10:43:43 +0900 > >Subject: [PATCH] mm: Use up free swap space before reaching OOM kill > > > >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. > >He said there was no problem when he disabled laptop_mode. > >The problem when I investigate problem is following as. > > > >Assumption for easy explanation: There are no page cache page in system > >because they all are already reclaimed. > > > >1. try_to_free_pages disable may_writepage when laptop_mode is enabled. > >2. shrink_inactive_list isolates victim pages from inactive anon lru list. > >3. shrink_page_list adds them to swapcache via add_to_swap but it doesn't > > pageout because sc->may_writepage is 0 so the page is rotated back into > > inactive anon lru list. The add_to_swap made the page Dirty by SetPageDirty. > >4. 3 couldn't reclaim any pages so do_try_to_free_pages increase priority and > > retry reclaim with higher priority. > >5. shrink_inactlive_list try to isolate victim pages from inactive anon lru list > > but got failed because it try to isolate pages with ISOLATE_CLEAN mode but > > inactive anon lru list is full of dirty pages by 3 so it just returns > > without any reclaim progress. > >6. do_try_to_free_pages doesn't set may_writepage due to zero total_scanned. > > Because sc->nr_scanned is increased by shrink_page_list but we don't call > > shrink_page_list in 5 due to short of isolated pages. > > > >Above loop is continued until OOM happens. > >The problem didn't happen before [1] was merged because old logic's > >isolatation in shrink_inactive_list was successful and tried to call > >shrink_page_list to pageout them but it still ends up failed to page out > >by may_writepage. But important point is that sc->nr_scanned was increased > >although we couldn't swap out them so do_try_to_free_pages could set > >may_writepages. > > > >Since [1] was introduced, it's not a good idea any more to depends on > >only the number of scanned pages for setting may_writepage. So this patch > >adds new trigger point of setting may_writepage as below DEF_PRIOIRTY - 2 > >which is used to show the significant memory pressure in VM so it's good > >fit for our purpose which would be better to lose power saving or clickety > >rather than OOM killing. > > > >[1] f80c067[mm: zone_reclaim: make isolate_lru_page() filter-aware] > > > >Reported-by: Luigi Semenzato <semenzato@xxxxxxxxxx> > >Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > > Your patch is a nice simplification. I am ok with the > change, provided it works for Luigi :) Thanks, Rik. Oops, I missed to Ccing Luigi. Add him again. Luigi, Could you test this patch? Thanks for your endless effort. > > Acked-by: Rik van Riel <riel@xxxxxxxxxx> > > > -- > All rights reversed > > -- > 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>