On Fri, Mar 27, 2026 at 12:12:04PM -0400, Zi Yan wrote: > On 27 Mar 2026, at 12:08, Lorenzo Stoakes (Oracle) wrote: > > So actually: > > > > | PF | MADV_COLLAPSE | khugepaged | > > |-----------|---------------|------------| > > large folio fs | ✓ | x | x | > > READ_ONLY_THP_FOR_FS | x | ✓ | ✓ | > > both! | ✓ | ✓ | ✓ | > > > > (Where it's impllied it's a read-only mapping obviously for the later two > > cases.) > > > > Now without READ_ONLY_THP_FOR_FS you're going to: > > > > | PF | MADV_COLLAPSE | khugepaged | > > |-----------|---------------|------------| > > large folio fs | ✓ | x | x | > > large folio + r/o | ✓ | ✓ | ✓ | > > > > And intentionally leaving behind the 'not large folio fs, r/o' case because > > those file systems need to implement large folio support. > > > > I guess we'll regress those users but we don't care? > > Yes. This also motivates FSes without large folio support to add large folio > support instead of relying on READ_ONLY_THP_FOR_FS hack.
Ack that's something I can back :) > > > > > I do think all this needs to be spelled out in the commit message though as > > it's > > subtle. > > > > Turns out this PitA config option is going to kick and scream a bit first > > before > > it goes... > > Sure. I will shameless steal your tables. Thank you for the contribution. ;) > Haha good I love to spread ASCII art :) Cheers, Lorenzo
