On Fri, Nov 13, 2020 at 03:55:39PM -0800, Andrew Morton wrote: > On Fri, 13 Nov 2020 09:34:48 -0800 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > When a process is being killed it might be in an uninterruptible sleep > > which leads to an unpredictable delay in its memory reclaim. In low memory > > situations, when it's important to free up memory quickly, such delay is > > problematic. Kernel solves this problem with oom-reaper thread which > > performs memory reclaim even when the victim process is not runnable. > > Userspace currently lacks such mechanisms and the need and potential > > solutions were discussed before (see links below). > > This patch provides a mechanism to perform memory reclaim in the context > > of the process that sends SIGKILL signal. New SYNC_REAP_MM flag for > > pidfd_send_signal syscall can be used only when sending SIGKILL signal > > and will lead to the caller synchronously reclaiming the memory that > > belongs to the victim and can be easily reclaimed. > > hm. > > Seems to me that the ability to reap another process's memory is a > generally useful one, and that it should not be tied to delivering a > signal in this fashion. I agree and I see you've already had some good ideas how to tie this to process_madvise(). If that's workable for your use-case then I'd prefer that approach. Signals are almost always not a great choice. Christian
