Messages in this thread | | | From | Vlastimil Babka <> | Subject | Re: [RFC PATCH 0/2] mm: fix OOMs for binding workloads to movable zone only node | Date | Thu, 5 Nov 2020 14:14:25 +0100 |
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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.
So if a process cannot is restricted to allocate from node X via cpuset *and* also cannot be executed on CPU's from node X via taskset, then it AFAICS effectively cannot violate the cpuset in SLUB because it won't reach the percpu or per-node caches that don't check cpusets.
>> But this >> stack shows that it went all the way to the page allocator, so the cpusets >> should have been obeyed there at least. > > Looking closer what is this dump_stack saying actually?
Yes, is that a dump of successful allocation (that violates cpusets?) or a failing one?
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