Hello, On Tue, Jan 27, 2015 at 12:03:34PM +0100, Vlastimil Babka wrote: > CC linux-mm in case somebody has a good answer but missed this in lkml traffic > > On 01/23/2015 11:18 PM, John Moser wrote: > > Why is there no tunable to OOM at low page cache? AFAIR, there were several trial although there wasn't acceptable at that time. One thing I can remember is min_filelist_kbytes. FYI, http://lwn.net/Articles/412313/ > > > > I have no swap configured. I have 16GB RAM. If Chrome or Gimp or some > > other stupid program goes off the deep end and eats up my RAM, I hit > > some 15.5GB or 15.75GB usage and stay there for about 40 minutes. Every > > time the program tries to do something to eat more RAM, it cranks disk > > hard; the disk starts thrashing, the mouse pointer stops moving, and > > nothing goes on. It's like swapping like crazy, except you're reading > > library files instead of paged anonymous RAM. > > > > If only I could tell the system to OOM kill at 512MB or 1GB or 95% > > non-evictable RAM, it would recover on its own. As-is, I need to wait > > or trigger the OOM killer by sysrq. > > > > Am I just the only person in the world who's ever had that problem? Or > > is it a matter of questions fast popping up when you try to do this > > *and* enable paging to disk? (In my experience, that's a matter of too > > much swap space: if you have 16GB RAM and your computer dies at 15.25GB > > usage, your swap space should be no larger than 750MB plus inactive > > working RAM; obviously, your computer can't handle paging 750MB back and > > forth. If you make it 8GB wide and you start swap thrashing at 2GB > > usage, you have too much swap available). > > > > I guess you could try to detect excessive swap and page cache thrashing, > > but that's complex; if anyone really wanted to do that, it would be done > > by now. A low-barrier OOM is much simpler. I'm far away from reclaim code for a long time but when I read again, I found something strange. With having swap in get_scan_count, we keep a mount of file LRU + free as above than high wmark to prevent file LRU thrashing but we don't with no swap. Why? Anyway, I believe we should fix it and we now have workingset.c so there might be more ways to be smart than old(although I am concern about that shadow shrinker blows out lots of information to be useful to detect in heavy memory pressure like page thrashing) Below could be band-aid until we find a elegant solution? >From c51787f7d75340b54bab2b5e3c587f4a483da51a Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@xxxxxxxxxx> Date: Wed, 28 Jan 2015 14:01:57 +0900 Subject: [PATCH] mm: prevent page thrashing No-Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> --- mm/vmscan.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 671e47edb584..b258df552e3a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2143,6 +2143,25 @@ out: denominator); break; case SCAN_FILE: + if (file && global_reclaim(sc)) { + unsigned long zonefile; + unsigned long zonefree; + + zonefree = zone_page_state(zone, + NR_FREE_PAGES); + zonefile = zone_page_state(zone, + NR_ACTIVE_FILE) + + zone_page_state(zone, + NR_INACTIVE_FILE); + + /* OOM is better than code thrashing */ + if (zonefile + zonefree <= + high_wmark_pages(zone)) { + size = 0; + scan = 0; + } + break; + } case SCAN_ANON: /* Scan one type exclusively */ if ((scan_balance == SCAN_FILE) != file) { -- 1.9.1 -- 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>