On Sat, Aug 19, 2023 at 11:49 AM David Ahern <dsahern@xxxxxxxxxx> wrote: > > On 8/19/23 9:22 AM, Jesper Dangaard Brouer wrote: > > > > I do see the problem of depending on having a struct page, as the > > page_pool_iov isn't related to struct page. Having "page" in the name > > of "page_pool_iov" is also confusing (hardest problem is CS is naming, > > as we all know). > > > > To support more allocator types, perhaps skb->pp_recycle bit need to > > grow another bit (and be renamed skb->recycle), so we can tell allocator > > types apart, those that are page based and those whom are not. > > > > > >> I think the feedback has been strong to not multiplex yet another > >> memory type into that struct, that is not a real page. Which is why > >> we went into this direction. This latest series limits the impact largely > >> to networking structures and code. > >> > > > > Some what related what I'm objecting to: the "page_pool_iov" is not a > > real page, but this getting recycled into something called "page_pool", > > which funny enough deals with struct-pages internally and depend on the > > struct-page-refcnt. > > > > Given the approach changed way from using struct page, then I also don't > > see the connection with the page_pool. Sorry. > > I do not care for the page_pool_iov name either; I presumed it was least > change to prove an idea and the name and details would evolve. > > How about something like buffer_pool or netdev_buf_pool that can operate > with either pages, dma addresses, or something else in the future? Sounds good. I suggested this name, but I see how using page in the name is not very clear. > > > >> As for the LSB trick: that avoided adding a lot of boilerplate churn > >> with new type and helper functions. > >> > > > > Says the lazy programmer :-P ... sorry could not resist ;-) :-) For the record, there is a prior version that added a separate type. I did not like the churn it brought and asked for this. > > Use of the LSB (or bits depending on alignment expectations) is a common > trick and already done in quite a few places in the networking stack. > This trick is essential to any realistic change here to incorporate gpu > memory; way too much code will have unnecessary churn without it. > > I do prefer my earlier suggestion though where the skb_frag_t has a > union of relevant types though. Instead of `struct page *page` it could > be `void *addr` with the helpers indicating page, iov, or other. Okay. I think that is how we did it previously.
