On Tue, Aug 20, 2019 at 2:31 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > [hmm the email got stuck on my send queue - sending again] > > On Mon 19-08-19 16:15:08, Yafang Shao wrote: > > On Mon, Aug 19, 2019 at 3:31 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Sun 18-08-19 00:24:54, Yafang Shao wrote: > > > > In the current memory.min design, the system is going to do OOM instead > > > > of reclaiming the reclaimable pages protected by memory.min if the > > > > system is lack of free memory. While under this condition, the OOM > > > > killer may kill the processes in the memcg protected by memory.min. > > > > > > Could you be more specific about the configuration that leads to this > > > situation? > > > > When I did memory pressure test to verify memory.min I found that issue. > > This issue can be produced as bellow, > > memcg setting, > > memory.max: 1G > > memory.min: 512M > > some processes are running is this memcg, with both serveral > > hundreds MB file mapping and serveral hundreds MB anon mapping. > > system setting, > > swap: off. > > some memory pressure test are running on the system. > > > > When the memory usage of this memcg is bellow the memory.min, the > > global reclaimers stop reclaiming pages in this memcg, and when > > there's no available memory, the OOM killer will be invoked. > > Unfortunately the OOM killer can chose the process running in the > > protected memcg. > > Well, the memcg protection was designed to prevent from regular > memory reclaim. It was not aimed at acting as a group wide oom > protection. The global oom killer (but memcg as well) simply cares only > about oom_score_adj when selecting a victim. > OOM is a kind of memory reclaim, isn't it ? > Adding yet another oom protection is likely to complicate the oom > selection logic and make it more surprising. E.g. why should workload > fitting inside the min limit be so special? Do you have any real world > example? > The problem here is we want to use it ini the real world, but the issuses we found prevent us from using it in the real world. > > In order to produce it easy, you can incease the memroy.min and set > > -1000 to the oom_socre_adj of the processes outside of the protected > > memcg. > > This sounds like a very dubious configuration to me. There is no other > option than chosing from the protected group. > This is only an easy example to produce it. > > Is this setting proper ? > > > > Thanks > > Yafang > > -- > Michal Hocko > SUSE Labs
