On Tue, Aug 13, 2019 at 04:14:32PM +0200, Michal Hocko wrote: [snip] > > > If the API is flawed then this is likely going > > > to kick us later and will be hard to fix. I am still not convinced about > > > the swap part of the thing TBH. > > > > Ok, then let us discuss it. As I mentioned before, without this we lose the > > access information due to MADVISE or swapping. Minchan and Konstantin both > > suggested it that's why I also added it (other than me also realizing that it > > is neeed). > > I have described my concerns about the general idle bit behavior after > unmapping pointing to discrepancy with !anon pages. And I believe those > haven't been addressed yet. You are referring to this post right? https://lkml.org/lkml/2019/8/6/637 Specifically your question was: How are you going to handle situation when the page is unmapped and refaulted again (e.g. a normal reclaim of a pagecache)? Currently I don't know how to implement that. Would it work if I stored the page-idle bit information in the pte of the file page (after the page is unmapped by reclaim?). Also, this could be a future extension - the Android heap profiler does not need it right now. I know that's not a good argument but it is useful to say that it doesn't affect a real world usecase.. the swap issue on the other hand, is a real usecase. Since the profiler should not get affected by swapping or MADVISE_COLD hints. > Besides that I am still not seeing any > description of the usecase that would suffer from the lack of the > functionality in changelogs. You are talking about the swap usecase? The usecase is well layed out in v5 2/6. Did you see it? https://lore.kernel.org/patchwork/patch/1112283/ thanks, - Joel
