On Thu, May 19, 2022 at 09:39:57AM +0200, Michal Hocko wrote: > On Thu 19-05-22 06:35:03, CGEL wrote: > > On Wed, May 18, 2022 at 02:14:28PM +0200, Michal Hocko wrote: > > > On Wed 18-05-22 07:40:30, CGEL wrote: > > > [...] > > > > 2. process_madvise is still a kind of madvise. processs_madvise from > > > > another process overrides the intention of origin app code ifself that > > > > also calls madvise, which is unrecoverable. For example, if a process "A" > > > > which madvises just one part of VMAs (not all) as MERGEABLE run on the OS > > > > already, meanwhile, if another process which doesn't know the information > > > > of "A" 's MERGEABLE areas, then call process_madvise to advise all VMAs of > > > > "A" as MERGEABLE, the original MERGEABLE information of "A" calling madivse > > > > is erasured permanently. > > > > > > I do not really follow. How is this any different from an external > > > process modifying the process wide policy via the proc or any other > > > interface? > > > > In this patch, you can see that we didn't modify the flag of any VMA of > > the target process, which is different from process_madvise. So it is > > easy to keep the original MERGEABLE information of the target process > > when we turn back to the default state from the state "always". > > This means that /proc/<pid>/smaps doesn't show the real state, right? Maybe we can add extra information of KSM forcible state in /proc/<pid>/smaps like THPeligible. Really, Michal, I think it again, 'process_ madvise' is really not good. In addition to some shortcomings I said before, If new vmas of the target process are created after the external process calls process_madvise(), then we have to call `process_madvise()` on them again, over and over again, regularly, just like Oleksandr said [1]. [1]: https://lore.kernel.org/lkml/1817008.tdWV9SEqCh@xxxxxxxxxxxxxx/ > > -- > Michal Hocko > SUSE Labs
