On Tue, May 21, 2019 at 08:24:21AM +0200, Michal Hocko wrote: > On Tue 21-05-19 11:48:20, Minchan Kim wrote: > > On Mon, May 20, 2019 at 11:22:58AM +0200, Michal Hocko wrote: > > > [Cc linux-api] > > > > > > On Mon 20-05-19 12:52:53, Minchan Kim wrote: > > > > Currently, process_madvise syscall works for only one address range > > > > so user should call the syscall several times to give hints to > > > > multiple address range. > > > > > > Is that a problem? How big of a problem? Any numbers? > > > > We easily have 2000+ vma so it's not trivial overhead. I will come up > > with number in the description at respin. > > Does this really have to be a fast operation? I would expect the monitor > is by no means a fast path. The system call overhead is not what it used > to be, sigh, but still for something that is not a hot path it should be > tolerable, especially when the whole operation is quite expensive on its > own (wrt. the syscall entry/exit). What's different with process_vm_[readv|writev] and vmsplice? If the range needed to be covered is a lot, vector operation makes senese to me. > > I am not saying we do not need a multiplexing API, I am just not sure > we need it right away. Btw. there was some demand for other MM syscalls > to provide a multiplexing API (e.g. mprotect), maybe it would be better > to handle those in one go? That's the exactly what Daniel Colascione suggested from internal review. That would be a interesting approach if we could aggregate all of system call in one go. > -- > Michal Hocko > SUSE Labs
