On Thu 05-11-20 14:14:25, Vlastimil Babka wrote: > On 11/5/20 1:58 PM, Michal Hocko wrote: > > On Thu 05-11-20 13:53:24, Vlastimil Babka wrote: > > > On 11/5/20 1:08 PM, Michal Hocko wrote: > > > > On Thu 05-11-20 09:40:28, Feng Tang wrote: > > > > > > > Could you be more specific? This sounds like a bug. Allocations > > > > > > shouldn't spill over to a node which is not in the cpuset. There are few > > > > > > exceptions like IRQ context but that shouldn't happen regurarly. > > > > > > > I mean when the docker starts, it will spawn many processes > > > which obey > > > > > the mem binding set, and they have some kernel page requests, which got > > > > > successfully allocated, like the following callstack: > > > > > > > [ 567.044953] CPU: 1 PID: 2021 Comm: runc:[1:CHILD] > > > Tainted: G W I 5.9.0-rc8+ #6 > > > > > [ 567.044956] Hardware name: /NUC6i5SYB, BIOS SYSKLi35.86A.0051.2016.0804.1114 08/04/2016 > > > > > [ 567.044958] Call Trace: > > > > > [ 567.044972] dump_stack+0x74/0x9a > > > > > [ 567.044978] __alloc_pages_nodemask.cold+0x22/0xe5 > > > > > [ 567.044986] alloc_pages_current+0x87/0xe0 > > > > > [ 567.044991] allocate_slab+0x2e5/0x4f0 > > > > > [ 567.044996] ___slab_alloc+0x380/0x5d0 > > > > > [ 567.045021] __slab_alloc+0x20/0x40 > > > > > [ 567.045025] kmem_cache_alloc+0x2a0/0x2e0 > > > > > [ 567.045033] mqueue_alloc_inode+0x1a/0x30 > > > > > [ 567.045041] alloc_inode+0x22/0xa0 > > > > > [ 567.045045] new_inode_pseudo+0x12/0x60 > > > > > [ 567.045049] new_inode+0x17/0x30 > > > > > [ 567.045052] mqueue_get_inode+0x45/0x3b0 > > > > > [ 567.045060] mqueue_fill_super+0x41/0x70 > > > > > [ 567.045067] vfs_get_super+0x7f/0x100 > > > > > [ 567.045074] get_tree_keyed+0x1d/0x20 > > > > > [ 567.045080] mqueue_get_tree+0x1c/0x20 > > > > > [ 567.045086] vfs_get_tree+0x2a/0xc0 > > > > > [ 567.045092] fc_mount+0x13/0x50 > > > > > [ 567.045099] mq_create_mount+0x92/0xe0 > > > > > [ 567.045102] mq_init_ns+0x3b/0x50 > > > > > [ 567.045106] copy_ipcs+0x10a/0x1b0 > > > > > [ 567.045113] create_new_namespaces+0xa6/0x2b0 > > > > > [ 567.045118] unshare_nsproxy_namespaces+0x5a/0xb0 > > > > > [ 567.045124] ksys_unshare+0x19f/0x360 > > > > > [ 567.045129] __x64_sys_unshare+0x12/0x20 > > > > > [ 567.045135] do_syscall_64+0x38/0x90 > > > > > [ 567.045143] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > > > > For it, the __alloc_pages_nodemask() will first try > > > process's targed > > > > > nodemask(unmovable node here), and there is no availabe zone, so it > > > > > goes with the NULL nodemask, and get a page in the slowpath. > > > > > OK, I see your point now. I was not aware of the slab allocator > > > not > > > > following cpusets. Sounds like a bug to me. > > > > > > SLAB and SLUB seem to not care about cpusets in the fast path. > > > > Is a fallback to a different node which is outside of the cpuset > > possible? > > AFAICS anything in per-cpu cache will be allocated without looking at the > cpuset, so it can be outside of the cpuset. In SLUB slowpath, > get_partial_node() looking for fallback on the same node will also not look > at cpuset. get_any_partial() looking for a fallback allocation on any node > does check cpuset_zone_allowed() and obey it strictly. A fallback to page > allocator will obey whatever page allocator obeys. IIUC this means that if there is no strong CPU binding to cpuset nodes then a runaway is possible. Albeit only partially and relying on somebody to fill up pcp object caches, right? Is that an overlook or a decision design or a performance optimization? -- Michal Hocko SUSE Labs
