On Fri 24-11-17 09:04:59, Minchan Kim wrote: > Shakeel Butt reported, he have observed in production system that > the job loader gets stuck for 10s of seconds while doing mount > operation. It turns out that it was stuck in register_shrinker() > and some unrelated job was under memory pressure and spending time > in shrink_slab(). Machines have a lot of shrinkers registered and > jobs under memory pressure has to traverse all of those memcg-aware > shrinkers and do affect unrelated jobs which want to register their > own shrinkers. > > To solve the issue, this patch simply bails out slab shrinking > once it found someone want to register shrinker in parallel. > A downside is it could cause unfair shrinking between shrinkers. > However, it should be rare and we can add compilcated logic once > we found it's not enough. > > Link: http://lkml.kernel.org/r/20171115005602.GB23810@bbox > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Reported-and-tested-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/vmscan.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 6a5a72baccd5..6698001787bd 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -486,6 +486,14 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, > sc.nid = 0; > > freed += do_shrink_slab(&sc, shrinker, priority); > + /* > + * bail out if someone want to register a new shrinker to > + * prevent long time stall by parallel ongoing shrinking. > + */ > + if (rwsem_is_contended(&shrinker_rwsem)) { > + freed = freed ? : 1; > + break; > + } > } > > up_read(&shrinker_rwsem); > -- > 2.7.4 > -- Michal Hocko SUSE Labs -- 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>
