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). However, the ability to apply other flavors of process_madvise() to large memory areas spanning multiple VMAs can be useful in more cases. For example in Android we will use process_madvise(MADV_PAGEOUT) to "shrink" an inactive background process. Today we have to read /proc/maps and construct the vector of VMAs even when applying this advice to the entire process. With such a special mode we could achieve this more efficiently and with less hussle. > -- > Michal Hocko > SUSE Labs
