On Wed 20-10-21 15:14:27, Vasily Averin wrote: > mem_cgroup_oom() can fail if current task was marked unkillable > and oom killer cannot find any victim. > > Currently we force memcg charge for such allocations, > however it allow memcg-limited userspace task in to overuse assigned limits > and potentially trigger the global memory shortage. You should really go into more details whether that is a practical problem to handle. OOM_FAILED means that the memcg oom killer couldn't find any oom victim so it cannot help with a forward progress. There are not that many situations when that can happen. Naming that would be really useful. > Let's fail the memory charge in such cases. > > This failure should be somehow recognised in #PF context, explain why > so let's use current->memcg_in_oom == (struct mem_cgroup *)OOM_FAILED > > ToDo: what is the best way to notify pagefault_out_of_memory() about > mem_cgroup_out_of_memory failure ? why don't you simply remove out_of_memory from pagefault_out_of_memory and leave it only with the blocking memcg OOM handling? Wouldn't that be a more generic solution? Your first patch already goes that way partially. This change is more risky than the first one. If somebody returns VM_FAULT_OOM without invoking allocator then it can loop for ever but invoking OOM killer in such a situation is equally wrong as the oom killer cannot really help, right? -- Michal Hocko SUSE Labs
