On Wed 18-11-20 11:22:21, Suren Baghdasaryan wrote: > On Wed, Nov 18, 2020 at 11:10 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Fri 13-11-20 18:16:32, Andrew Morton wrote: > > [...] > > > It's all sounding a bit painful (but not *too* painful). But to > > > reiterate, I do think that adding the ability for a process to shoot > > > down a large amount of another process's memory is a lot more generally > > > useful than tying it to SIGKILL, agree? > > > > I am not sure TBH. Is there any reasonable usecase where uncoordinated > > memory tear down is OK and a target process which is able to see the > > unmapped memory? > > I think uncoordinated memory tear down is a special case which makes > sense only when the target process is being killed (and we can enforce > that by allowing MADV_DONTNEED to be used only if the target process > has pending SIGKILL). That would be safe but then I am wondering whether it makes sense to implement as a madvise call. It is quite strange to expect somebody call a syscall on a killed process. But this is more a detail. I am not a great fan of a more generic MADV_DONTNEED on a remote process. This is just too dangerous IMHO. > However, the ability to apply other flavors of > process_madvise() to large memory areas spanning multiple VMAs can be > useful in more cases. Yes I do agree with that. The error reporting would be more tricky but I am not really sure that the exact reporting is really necessary for advice like interface. > For example in Android we will use > process_madvise(MADV_PAGEOUT) to "shrink" an inactive background > process. That makes sense to me. -- Michal Hocko SUSE Labs
