Hi Andrew,
it turned out that this is not a theoretical issue after all. Trevor
(added to the CC) was seeing pre-mature OOM killer triggering [1]
bisected to b2e18757f2c9 ("mm, vmscan: begin reclaiming pages on a
per-node basis").
After some going back and forth it turned out that b4536f0c829c ("mm,
memcg: fix the active list aging for lowmem requests when memcg is
enabled") helped a lot but it wasn't sufficient on its own. We also
need this patch to make the oom behavior stable again. So I suggest
backporting this to stable as well. Could you update the changelog as
follows?The patch would need to be tweaked a bit to apply to 4.10 and older but I will do that as soon as it hits the Linus tree in the next merge window. [1] http://lkml.kernel.org/r/[email protected] On Tue 17-01-17 11:37:01, Michal Hocko wrote: > From: Michal Hocko <[email protected]> > > get_scan_count considers the whole node LRU size when > - doing SCAN_FILE due to many page cache inactive pages > - calculating the number of pages to scan > > in both cases this might lead to unexpected behavior especially on 32b > systems where we can expect lowmem memory pressure very often. > > A large highmem zone can easily distort SCAN_FILE heuristic because > there might be only few file pages from the eligible zones on the node > lru and we would still enforce file lru scanning which can lead to > trashing while we could still scan anonymous pages. > > The later use of lruvec_lru_size can be problematic as well. Especially > when there are not many pages from the eligible zones. We would have to > skip over many pages to find anything to reclaim but shrink_node_memcg > would only reduce the remaining number to scan by SWAP_CLUSTER_MAX > at maximum. Therefore we can end up going over a large LRU many times > without actually having chance to reclaim much if anything at all. The > closer we are out of memory on lowmem zone the worse the problem will > be. > > Fix this by filtering out all the ineligible zones when calculating the > lru size for both paths and consider only sc->reclaim_idx zones. > Fixes: b2e18757f2c9 ("mm, vmscan: begin reclaiming pages on a per-node basis") Cc: stable # 4.8+ Tested-by: Trevor Cordes <[email protected]> > Acked-by: Minchan Kim <[email protected]> > Acked-by: Hillf Danton <[email protected]> > Signed-off-by: Michal Hocko <[email protected]> > --- > mm/vmscan.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index aed39dc272c0..ffac8fa7bdd8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2235,7 +2235,7 @@ static void get_scan_count(struct lruvec *lruvec, > struct mem_cgroup *memcg, > * system is under heavy pressure. > */ > if (!inactive_list_is_low(lruvec, true, sc, false) && > - lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES) >> > sc->priority) { > + lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> > sc->priority) { > scan_balance = SCAN_FILE; > goto out; > } > @@ -2302,7 +2302,7 @@ static void get_scan_count(struct lruvec *lruvec, > struct mem_cgroup *memcg, > unsigned long size; > unsigned long scan; > > - size = lruvec_lru_size(lruvec, lru, MAX_NR_ZONES); > + size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); > scan = size >> sc->priority; > > if (!scan && pass && force_scan) > -- > 2.11.0 > -- Michal Hocko SUSE Labs
