On Fri, Sep 17, 2021 at 12:31:36PM -0400, Johannes Weiner wrote: > I didn't suggest to change what the folio currently already is for the > page cache. I asked to keep anon pages out of it (and in the future > potentially other random stuff that is using compound pages). It would mean that anon-THP cannot benefit from the work Willy did with folios. Anon-THP is the most active user of compound pages at the moment and it also suffers from the compound_head() plague. You ask to exclude anon-THP siting *possible* future benefits for pagecache. Sorry, but this doesn't sound fair to me. We already had similar experiment with PAGE_CACHE_SIZE. It was introduced with hope to have PAGE_CACHE_SIZE != PAGE_SIZE one day. It never happened and only caused confusion on the border between pagecache-specific code and generic code that handled both file and anon pages. If you want to limit usage of the new type to pagecache, the burden on you to prove that it is useful and not just a dead weight. -- Kirill A. Shutemov
