On Thu, Nov 05, 2020 at 05:16:12PM +0100, Michal Hocko wrote: > On Thu 05-11-20 21:43:05, Feng Tang wrote: > > On Thu, Nov 05, 2020 at 02:12:45PM +0100, Michal Hocko wrote: > > > On Thu 05-11-20 21:07:10, Feng Tang wrote: > > > [...] > > > > My debug traces shows it is, and its gfp_mask is 'GFP_KERNEL' > > > > > > Can you provide the full information please? Which node has been > > > requested. Which cpuset the calling process run in and which node has > > > the allocation succeeded from? A bare dump_stack without any further > > > context is not really helpful. > > > > I don't have the same platform as the original report, so I simulated > > one similar setup (with fakenuma and movablecore), which has 2 memory > > nodes: node 0 has DMA0/DMA32/Movable zones, while node 1 has only > > Movable zone. With it, I can got the same error and same oom callstack > > as the original report (as in the cover-letter). > > > > The test command is: > > # docker run -it --rm --cpuset-mems 1 ubuntu:latest bash -c "grep Mems_allowed /proc/self/status" > > > > To debug I only added some trace in the __alloc_pages_nodemask(), and > > for the callstack which get the page successfully: > > > > [ 567.510903] Call Trace: > > [ 567.510909] dump_stack+0x74/0x9a > > [ 567.510910] __alloc_pages_nodemask.cold+0x22/0xe5 > > [ 567.510913] alloc_pages_current+0x87/0xe0 > > [ 567.510914] __vmalloc_node_range+0x14c/0x240 > > [ 567.510918] module_alloc+0x82/0xe0 > > [ 567.510921] bpf_jit_alloc_exec+0xe/0x10 > > [ 567.510922] bpf_jit_binary_alloc+0x7a/0x120 > > [ 567.510925] bpf_int_jit_compile+0x145/0x424 > > [ 567.510926] bpf_prog_select_runtime+0xac/0x130 > > As already said this doesn't really tell much without the additional > information. > > > The incomming parameter nodemask is NULL, and the function will first try the > > cpuset nodemask (1 here), and the zoneidx is only granted 2, which makes the > > 'ac's preferred zone to be NULL. so it goes into __alloc_pages_slowpath(), > > which will first set the nodemask to 'NULL', and this time it got a preferred > > zone: zone DMA32 from node 0, following get_page_from_freelist will allocate > > one page from that zone. > > I do not follow. Both hot and slow paths of the allocator set > ALLOC_CPUSET or emulate it by mems_allowed when cpusets are nebaled > IIRC. This is later enforced in get_page_from_free_list. There are some > exceptions when the allocating process can run away from its cpusets - > e.g. IRQs, OOM victims and few other cases but definitely not a random > allocation. There might be some subtle details that have changed or I > might have forgot but yes, I was confused too. IIUC, the key check inside get_page_from_freelist() is if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) && !__cpuset_zone_allowed(zone, gfp_mask)) In our case (kernel page got allocated), the first 2 conditions are true, and for __cpuset_zone_allowed(), the possible place to return true is checking parent cpuset's nodemask cs = nearest_hardwall_ancestor(task_cs(current)); allowed = node_isset(node, cs->mems_allowed); This will override the ALLOC_CPUSET check. Thanks, Feng > -- > Michal Hocko > SUSE Labs
