On Wed, Feb 24, 2021 at 03:34:16PM -0700, Yu Zhao wrote: > > If only somebody were working on a patch series to get rid of > > all those calls to compound_head()! Some reviews on > > https://lore.kernel.org/linux-mm/20210128070404.1922318-2-wi...@infradead.org/ > > would be nice. > > I'm on board with the idea and have done some research in this > direction. We've found that the ideal *anon* page size for Chrome OS > is not 4KB or 2MB, but 32KB. I hope we could leverage the folio to > support flexible anon page size to reduce the number of page faults > (vs 4KB) or internal fragmentation (vs 2MB). > > That being said, it seems to me this is a long term plan and right > now we need something smaller. So if you don't mind, I'll just go > ahead and remove compound_head() from Page{LRU,Active,Unevictable, > SwapBacked} first?
It's really not a big change I'm suggesting here. You need https://lore.kernel.org/linux-mm/20210128070404.1922318-2-wi...@infradead.org/ https://lore.kernel.org/linux-mm/20210128070404.1922318-5-wi...@infradead.org/ https://lore.kernel.org/linux-mm/20210128070404.1922318-8-wi...@infradead.org/ and then the patch I sent above to create folio_lru(). Then any changes you want to make to use folios more broadly will incrementally move us towards your goal of 32kB anon pages.
