On Wed, Mar 11, 2020 at 7:04 PM Daniel Colascione <dancol@xxxxxxxxxx> wrote: > > On Wed, Mar 11, 2020 at 5:18 PM Minchan Kim <minchan@xxxxxxxxxx> wrote: > > > > On Wed, Mar 11, 2020 at 04:53:17PM -0700, Shakeel Butt wrote: > > > On Wed, Mar 11, 2020 at 1:45 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > > > > > On Tue 10-03-20 15:48:31, Dave Hansen wrote: > > > > > Maybe instead of just punting on MADV_PAGEOUT for map_count>1 we should > > > > > only let it affect the *local* process. We could still put the page in > > > > > the swap cache, we just wouldn't go do the rmap walk. > > > > > > > > Is it really worth medling with the reclaim code and special case > > > > MADV_PAGEOUT there? I mean it is quite reasonable to have an initial > > > > implementation that doesn't really touch shared pages because that can > > > > lead to all sorts of hard to debug and unexpected problems. So I would > > > > much rather go with a simple patch to check map count first and see > > > > whether somebody actually cares about those shared pages and go from > > > > there. > > > > > > > > Minchan, do you want to take my diff and turn it into the proper patch > > > > or should I do it. > > > > > > > > > > What about the remote_madvise(MADV_PAGEOUT)? Will your patch disable > > > the pageout from that code path as well for pages with mapcount > 1? > > > > Maybe, not because process_madvise syscall needs more previliedge(ie, > > PTRACE_MODE_ATTACH_FSCREDS) so I guess it would be more secure. > > So in that case, I want to rely on the LRU chance for shared pages. > > I don't want the behavior of an madvise command to change depending on > *how* the command is invoked. MADV_PAGEOUT should do the same thing > regardless. If you want to allow purging of shared pages as well, > please add a new MADV_PAGEOUT_ALL or something and require a privilege > to use it. > I would like to have a way to pageout the shared pages and MADV_PAGEOUT_ALL approach looks fine to me.
