On 02/10/2023 13:58, David Hildenbrand wrote: >> [...] >> >> My concern is that the "fresh start" is not as simple as it appears. I've come >> to the conclusion that if we have a new interface, then it should really be a >> strict superset of THP to make it extensible in future. But that opens questions > > ^ +1 > >> about how you configure PMD-sized allocations when both interfaces disagree. For >> "enabled" its fairly straightforward; you can do a logical OR. But its less >> clear how to handle disagreement over defrag. And then you have huge_zero_page >> and khugepaged etc, which might just stay with THP. But eventually we will > > Probably we want everything that THP had (khugepaged, zeropage, ...) also on > some (selected?) smaller orders. > >> probably want to do async collapse for smaller order folios too, and at that >> point you have to duplicate all those controls... So I concluded that actually >> it is cleaner to just bolt on a small-order extension to THP. I've updated all >> the docs, and that was pretty simple to do, which usually suggests that the >> extension is purely additive and shouldn't be confusing. > > Fine with me. I don't quite like bitmaps exposed to user space, though. Just > having a user-readable list or a "directory" with various options as files might > be cleaner ... > >> >> Take a look at the patches, then make a judgement ;-) >> > > ... but we'll discuss it there :) > David, FYI, the patches are posted at [1] (you're cc'ed) and have been in mm-unstable for nearly a week - so I guess they will go to mm-stable soon by default. So if you want to object to any of it, now's the time ;-). [1] https://lore.kernel.org/linux-mm/20230929114421.3761121-1-ryan.roberts@xxxxxxx/
