On Fri, May 23, 2014 at 01:51:12PM -0700, David Rientjes wrote: > On Fri, 23 May 2014, Marcelo Tosatti wrote: > > > Zone specific allocations, such as GFP_DMA32, should not be restricted > > to cpusets allowed node list: the zones which such allocations demand > > might be contained in particular nodes outside the cpuset node list. > > > > The alternative would be to not perform such allocations from > > applications which are cpuset restricted, which is unrealistic. > > > > Or ensure applications that allocate from lowmem are allowed to do so, but > I understand that might be hard to make sure always happens. > > > Fixes KVM's alloc_page(gfp_mask=GFP_DMA32) with cpuset as explained. > > > > Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 5dba293..f228039 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -2698,6 +2698,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, > > unsigned int cpuset_mems_cookie; > > int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR; > > struct mem_cgroup *memcg = NULL; > > + nodemask_t *cpuset_mems_allowed = &cpuset_current_mems_allowed; > > > > gfp_mask &= gfp_allowed_mask; > > > > @@ -2726,9 +2727,14 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, > > retry_cpuset: > > cpuset_mems_cookie = read_mems_allowed_begin(); > > > > +#ifdef CONFIG_NUMA > > + if (gfp_zone(gfp_mask) < policy_zone) > > + cpuset_mems_allowed = NULL; > > +#endif > > + > > /* The preferred zone is used for statistics later */ > > first_zones_zonelist(zonelist, high_zoneidx, > > - nodemask ? : &cpuset_current_mems_allowed, > > + nodemask ? : cpuset_mems_allowed, > > &preferred_zone); > > if (!preferred_zone) > > goto out; > > > > I think this is incomplete. Correct me if I'm wrong on how this is > working: preferred_zone, today, is NULL because first_zones_zonelist() is > restricted to a cpuset.mems that does not include lowmem and your patch > fixes that. > But if the fastpath allocation with mandatory ALLOC_CPUSET > fails and we go to the slowpath, which may or may not have showed up in > your testing, there's still issues, > particularly if __GFP_WAIT and lots of > allocators do GFP_KERNEL | __GFP_DMA32. This requires ALLOC_CPUSET on all > allocations and you haven't updated __cpuset_node_allowed_softwall() with > this exception nor zlc_setup(). Yes, thanks. Can you please review updated patch below. > After that's done, I think all of this is really convoluted and deserves a > comment to describe the ALLOC_CPUSET and __GFP_DMA32 behavior. The comment at mm/mempolicy.c seems sufficient: /* Highest zone. An specific allocation for a zone below that is not policied. */ enum zone_type policy_zone = 0; > Adding Li, the cpusets maintainer, to this as well. diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 3d54c41..b70a336 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2392,6 +2392,10 @@ int __cpuset_node_allowed_softwall(int node, gfp_t gfp_mask) if (in_interrupt() || (gfp_mask & __GFP_THISNODE)) return 1; +#ifdef CONFIG_NUMA + if (gfp_zone(gfp_mask) < policy_zone) + return 1; +#endif might_sleep_if(!(gfp_mask & __GFP_HARDWALL)); if (node_isset(node, current->mems_allowed)) return 1; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5dba293..dfea3dc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2698,6 +2698,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, unsigned int cpuset_mems_cookie; int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR; struct mem_cgroup *memcg = NULL; + nodemask_t *cpuset_mems_allowed = &cpuset_current_mems_allowed; gfp_mask &= gfp_allowed_mask; @@ -2726,9 +2727,14 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, retry_cpuset: cpuset_mems_cookie = read_mems_allowed_begin(); +#ifdef CONFIG_NUMA + if (gfp_zone(gfp_mask) < policy_zone) + cpuset_mems_allowed = NULL; +#endif + /* The preferred zone is used for statistics later */ first_zones_zonelist(zonelist, high_zoneidx, - nodemask ? : &cpuset_current_mems_allowed, + nodemask ? : cpuset_mems_allowed, &preferred_zone); if (!preferred_zone) goto out; -- 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>