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). 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? -- Michal Hocko SUSE Labs
