Hi Yosry, glad to hear from you and happy new year! > Sorry for being late to the party. It seems to me that all of this > hassle can be avoided if lru_add_fn() did the right thing in this case > and added the folio to the tail of the lru directly. I am no expert in > how the page flags work here, but it seems like we can do something > like this in lru_add_fn(): > > if (folio_test_reclaim(folio)) > lruvec_add_folio_tail(lruvec, folio); > else > lruvec_add_folio(lruvec, folio); > > I think the main problem with this is that PG_reclaim is an alias to > PG_readahead, so readahead pages will also go to the tail of the lru, > which is probably not good. Agree with you， I will try it. > > A more intrusive alternative is to introduce a folio_lru_add_tail() > variant that always adds pages to the tail, and optionally call that > from __read_swap_cache_async() instead of folio_lru_add() based on a > new boolean argument. The zswap code can set that boolean argument > during writeback to make sure newly allocated folios are always added > to the tail of the lru. I have the same idea and also find it intrusive. I think the first solution is very good and I will try it. If it works, I will send the next version. Thank you very much.
