On Mon, 2018-02-12 at 12:05 -0800, Tejun Heo wrote: > On Mon, Feb 12, 2018 at 09:03:25AM -0800, Tejun Heo wrote: > > Hello, Daniel. > > > > On Mon, Feb 12, 2018 at 06:00:13PM +0100, Daniel Borkmann wrote: > > > [ +Dennis, +Tejun ] > > > > > > Looks like we're stuck in percpu allocator with key/value size of 4 bytes > > > each and large number of entries (max_entries) in the reproducer in above > > > link. > > > > > > Could we have some __GFP_NORETRY semantics and let allocations fail > > > instead > > > of triggering OOM killer? > > > > For some part, maybe, but not generally. The virt area allocation > > goes down to page table allocation which is hard coded to use > > GFP_KERNEL in arch mm code. > > So, the following should convert majority of allocations to use > __GFP_NORETRY. It doesn't catch everything but should significantly > lower the probability of hitting this and put this on the same footing > as vmalloc. Can you see whether this is enough? > > Note that this patch isn't upstreamable. We definitely want to > restrict this to the rebalance path, but it should be good enough for > testing. > > Thanks. > > diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c > index 9158e5a..0b4739f 100644 > --- a/mm/percpu-vm.c > +++ b/mm/percpu-vm.c > @@ -81,7 +81,7 @@ static void pcpu_free_pages(struct pcpu_chunk *chunk, > static int pcpu_alloc_pages(struct pcpu_chunk *chunk, > struct page **pages, int page_start, int page_end) > { > - const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM; > + const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_NORETRY; > unsigned int cpu, tcpu; > int i; >
Also I would consider using this fix as I had warnings of cpus being stuck there for more than 50 ms : diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c index 9158e5a81391ced4e268e3d5dd9879c2bc7280ce..6309b01ceb357be01e857e5f899429403836f41f 100644 --- a/mm/percpu-vm.c +++ b/mm/percpu-vm.c @@ -92,6 +92,7 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk, *pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0); if (!*pagep) goto err; + cond_resched(); } } return 0;