On Thu, Apr 11, 2019 at 10:09 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Thu, Apr 11, 2019 at 8:33 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > On Wed, Apr 10, 2019 at 06:43:53PM -0700, Suren Baghdasaryan wrote: > > > Add new SS_EXPEDITE flag to be used when sending SIGKILL via > > > pidfd_send_signal() syscall to allow expedited memory reclaim of the > > > victim process. The usage of this flag is currently limited to SIGKILL > > > signal and only to privileged users. > > > > What is the downside of doing expedited memory reclaim? ie why not do it > > every time a process is going to die? > > I think with an implementation that does not use/abuse oom-reaper > thread this could be done for any kill. As I mentioned oom-reaper is a > limited resource which has access to memory reserves and should not be > abused in the way I do in this reference implementation. > While there might be downsides that I don't know of, I'm not sure it's > required to hurry every kill's memory reclaim. I think there are cases > when resource deallocation is critical, for example when we kill to > relieve resource shortage and there are kills when reclaim speed is > not essential. It would be great if we can identify urgent cases > without userspace hints, so I'm open to suggestions that do not > involve additional flags. I was imagining a PI-ish approach where we'd reap in case an RT process was waiting on the death of some other process. I'd still prefer the API I proposed in the other message because it gets the kernel out of the business of deciding what the right signal is. I'm a huge believer in "mechanism, not policy".
