Matthew Wilcox <willy@xxxxxxxxxxxxx> writes: > On Mon, Mar 10, 2025 at 06:26:23PM +0100, Toke Høiland-Jørgensen wrote: >> Matthew Wilcox <willy@xxxxxxxxxxxxx> writes: >> > See https://kernelnewbies.org/MatthewWilcox/Memdescs >> > and more immediately >> > https://kernelnewbies.org/MatthewWilcox/Memdescs/Path >> > >> > pagepool is going to be renamed "bump" because it's a bump allocator and >> > "pagepool" is a nonsense name. I haven't looked into it in a lot of >> > detail yet, but in the not-too-distant future, struct page will look >> > like this (from your point of view): >> > >> > struct page { >> > unsigned long flags; >> > unsigned long memdesc; >> > int _refcount; // 0 for bump >> > union { >> > unsigned long private; >> > atomic_t _mapcount; // maybe used by bump? not sure >> > }; >> > }; >> > >> > 'memdesc' will be a pointer to struct bump with the bottom four bits of >> > that pointer indicating that it's a struct bump pointer (and not, say, a >> > folio or a slab). >> > >> > So if you allocate a multi-page bump, you'll get N of these pages, >> > and they'll all point to the same struct bump where you'll maintain >> > your actual refcount. And you'll be able to grow struct bump to your >> > heart's content. I don't know exactly what struct bump looks like, >> > but the core mm will have no requirements on you. >> >> Ah, excellent, thanks for the pointer! >> >> Out of curiosity, why "bump"? Is that a term of art somewhere? > > https://en.wikipedia.org/wiki/Region-based_memory_management > > (and the term "bump allocator" has a number of hits in your favourite > search engine) Right, fair point, I was being lazy by just asking. Thanks for taking the time to provide a link :) >> And in the meantime (until those patches land), do you see any reason >> why we can't squat on the middle bits of page->pp_magic (AKA page->lru) >> like I'm doing in v2[0] of this patch? > > I haven't had time to dig into this series. I'm trying to get a bunch > of things finished before LSFMM. Alright, well if/when you get a chance (before of after LSFMM), I'd appreciate if you could take a look! -Toke
