On Tue 05-10-21 16:52:40, Vasily Averin wrote: > Huge vmalloc allocation on heavy loaded node can lead to a global > memory shortage. Task called vmalloc can have worst badness and > be selected by OOM-killer, however taken fatal signal does not > interrupt allocation cycle. Vmalloc repeat page allocaions > again and again, exacerbating the crisis and consuming the memory > freed up by another killed tasks. > > After a successful completion of the allocation procedure, a fatal > signal will be processed and task will be destroyed finally. > However it may not release the consumed memory, since the allocated > object may have a lifetime unrelated to the completed task. > In the worst case, this can lead to the host will panic > due to "Out of memory and no killable processes..." > > This patch allows OOM-killer to break vmalloc cycle, makes OOM more > effective and avoid host panic. It does not check oom condition directly, > however, and breaks page allocation cycle when fatal signal was received. This will allow also interrupting a user space requist which happens to trigger a large vmalloc, hence the reason for going for fatal_signal_pending rather than oom specific condition. > This may trigger some hidden problems, when caller does not handle > vmalloc failures, or when rollaback after failed vmalloc calls own > vmallocs inside. However all of these scenarios are incorrect: > vmalloc does not guarantee successful allocation, it has never been called > with __GFP_NOFAIL and threfore either should not be used for any rollbacks > or should handle such errors correctly and not lead to critical > failures. __GFP_NOFAIL semantic is explicitly not supported for vmalloc. > Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> I would keep it sitting in the linux-next for some time to sort out potential fallouts and have them fixed before this one gets merged. Thanks! > --- > v2: tsk_is_oom_victim() check replaced by fatal_signal_pending(current), > removed check inside __alloc_pages_bulk(), > according to feedback from mhocko@. > Updated patch description. > --- > mm/vmalloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d77830ff604c..71706f5447f0 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2860,6 +2860,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid, > struct page *page; > int i; > > + if (fatal_signal_pending(current)) > + break; > + > page = alloc_pages_node(nid, gfp, order); > if (unlikely(!page)) > break; > -- > 2.31.1 -- Michal Hocko SUSE Labs
