On Mon 18-10-21 11:13:52, Vasily Averin wrote: [...] > How could this happen? > > User-space task inside the memcg-limited container generated a page fault, > its handler do_user_addr_fault() called handle_mm_fault which could not > allocate the page due to exceeding the memcg limit and returned VM_FAULT_OOM. > Then do_user_addr_fault() called pagefault_out_of_memory() which executed > out_of_memory() without set of memcg. > > Partially this problem depends on one of my recent patches, disabled unlimited > memory allocation for dying tasks. However I think the problem can happen > on non-killed tasks too, for example because of kmem limit. Could you be more specific on how this can happen without your patch? I have to say I haven't realized this side effect when discussing it. I will be honest that I am not really happy about pagefault_out_of_memory. I have tried to remove it in the past. Without much success back then, unfortunately[1]. Maybe we should get rid of it finally. The OOM is always triggered from inside the allocator where we have much more infromation about the allocation context. A first step would be to skip pagefault_out_of_memory for killed or exiting processes. [1] I do not have msg-id so I cannot provide a lore link but google pointed me to https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1400402.html -- Michal Hocko SUSE Labs
