On Thu, Apr 11, 2019 at 12:51:11PM +0200, Michal Hocko wrote: > I would question whether we really need this at all? Relying on the exit > speed sounds like a fundamental design problem of anything that relies > on it. Sure task exit might be slow, but async mm tear down is just a > mere optimization this is not guaranteed to really help in speading > things up. OOM killer uses it as a guarantee for a forward progress in a > finite time rather than as soon as possible. I don't think it's flawed, it's just optimizing the user experience as best as it can. You don't want to kill things prematurely, but once there is pressure you want to rectify it quickly. That's valid. We have a tool that does this, side effect or not, so I think it's fair to try to make use of it when oom killing from userspace (which we explictily support with oom_control in cgroup1 and memory.high in cgroup2, and it's not just an Android thing). The question is how explicit a contract we want to make with userspace, and I would much prefer to not overpromise on a best-effort thing like this, or even making the oom reaper ABI. If unconditionally reaping killed tasks is too expensive, I'd much prefer a simple kill hint over an explicit task reclaim interface.
