Hey Matthew, Thanks for taking time to review. On Wed, Apr 24, 2024 at 12:15 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Mon, Apr 22, 2024 at 01:52:13PM +0800, Lance Yang wrote: > > When the user no longer requires the pages, they would use > > madvise(MADV_FREE) to mark the pages as lazy free. IMO, they would not > > typically rewrite to the given range. > > > > At present, PMD-mapped THPs that are marked as lazyfree during > > shrink_folio_list() are unconditionally split, which may be unnecessary. > > If the THP is clean, its PMD is also clean, and there are no unexpected "If the THP is clean, its PMD is also clean" can be confusing - sorry. It should be modified to "If the THP and its PMD are both marked as clean". Thanks, Lance > > references, then we can attempt to remove the PMD mapping from it. This > > change will improve the efficiency of memory reclamation in this case. > > Does this happen outside of benchmarks? I'm really struggling to see > how we end up in this situation. We have a clean THP without swap > backing, so it's full of zeroes, but for some reason we haven't used the > shared huge zero page? What is going on? >
