Hi Eric, On Tue, Feb 13, 2018 at 05:35:26AM -0800, Eric Dumazet wrote: > > 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; > >
This function gets called from pcpu_populate_chunk while holding the pcpu_alloc_mutex and is called from two scenarios. First, when an allocation occurs to a place without backing pages, and second when the workqueue item is scheduled to replenish the number of empty pages. So, I don't think this is a good idea. My understanding is if we're seeing warnings here, that means we're struggling to find backing pages. I believe adding __GFP_NORETRY on the workqueue path as Tejun mentioned above would help with warnings as well, but not if they are caused by the allocation path. Thanks, Dennis
