On Thu, Nov 16, 2023 at 1:09 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > > On 11/15/2023 6:26 AM, Yafang Shao wrote: > > On Wed, Nov 15, 2023 at 5:33 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > >> On Wed, Nov 15, 2023 at 4:45 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > >>> On Wed 15-11-23 09:52:38, Yafang Shao wrote: > >>>> On Wed, Nov 15, 2023 at 12:58 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > >>>>> On 11/14/2023 3:59 AM, Yafang Shao wrote: > >>>>>> On Tue, Nov 14, 2023 at 6:15 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > >>>>>>> On Mon 13-11-23 11:15:06, Yafang Shao wrote: > >>>>>>>> On Mon, Nov 13, 2023 at 12:45 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > >>>>>>>>> On 11/11/2023 11:34 PM, Yafang Shao wrote: > >>>>>>>>>> Background > >>>>>>>>>> ========== > >>>>>>>>>> > >>>>>>>>>> In our containerized environment, we've identified unexpected OOM events > >>>>>>>>>> where the OOM-killer terminates tasks despite having ample free memory. > >>>>>>>>>> This anomaly is traced back to tasks within a container using mbind(2) to > >>>>>>>>>> bind memory to a specific NUMA node. When the allocated memory on this node > >>>>>>>>>> is exhausted, the OOM-killer, prioritizing tasks based on oom_score, > >>>>>>>>>> indiscriminately kills tasks. This becomes more critical with guaranteed > >>>>>>>>>> tasks (oom_score_adj: -998) aggravating the issue. > >>>>>>>>> Is there some reason why you can't fix the callers of mbind(2)? > >>>>>>>>> This looks like an user space configuration error rather than a > >>>>>>>>> system security issue. > >>>>>>>> It appears my initial description may have caused confusion. In this > >>>>>>>> scenario, the caller is an unprivileged user lacking any capabilities. > >>>>>>>> While a privileged user, such as root, experiencing this issue might > >>>>>>>> indicate a user space configuration error, the concerning aspect is > >>>>>>>> the potential for an unprivileged user to disrupt the system easily. > >>>>>>>> If this is perceived as a misconfiguration, the question arises: What > >>>>>>>> is the correct configuration to prevent an unprivileged user from > >>>>>>>> utilizing mbind(2)?" > >>>>>>> How is this any different than a non NUMA (mbind) situation? > >>>>>> In a UMA system, each gigabyte of memory carries the same cost. > >>>>>> Conversely, in a NUMA architecture, opting to confine processes within > >>>>>> a specific NUMA node incurs additional costs. In the worst-case > >>>>>> scenario, if all containers opt to bind their memory exclusively to > >>>>>> specific nodes, it will result in significant memory wastage. > >>>>> That still sounds like you've misconfigured your containers such > >>>>> that they expect to get more memory than is available, and that > >>>>> they have more control over it than they really do. > >>>> And again: What configuration method is suitable to limit user control > >>>> over memory policy adjustments, besides the heavyweight seccomp > >>>> approach? > > What makes seccomp "heavyweight"? The overhead? The infrastructure required? > > >>> This really depends on the workloads. What is the reason mbind is used > >>> in the first place? > >> It can improve their performance. > > How much? You've already demonstrated that using mbind can degrade their performance. Pls. calm down and read the whole discussion carefully. It is not easy to understand. -- Regards Yafang
