(-cc invalid emails) Replying to my self here but.... [...] > > > > > > We can't do that. The reason we need those structs is that we rely on the > > > existing XDP code, which already recycles it's buffers, to enable > > > recycling. Since we allocate a page per packet when using page_pool for a > > > driver , the same ideas apply to an SKB and XDP frame. We just recycle the > > > > I am not really familar with XDP here, but a packet from hw is either a > > "struct xdp_frame/xdp_buff" for XDP or a "struct sk_buff" for TCP/IP stack, > > a packet can not be both "struct xdp_frame/xdp_buff" and "struct sk_buff" at > > the same time, right? > > > > Yes, but the payload is irrelevant in both cases and that's what we use > page_pool for. You can't use this patchset unless your driver usues > build_skb(). So in both cases you just allocate memory for the payload and > decide what the wrap the buffer with (XDP or SKB) later. > > > What does not really make sense to me is that the page has to be from page > > pool when a skb's frag page can be recycled, right? If it is ture, the switch > > case in __xdp_return() does not really make sense for skb recycling, why go > > all the trouble of checking the mem->type and mem->id to find the page_pool > > pointer when recyclable page for skb can only be from page pool? > > In any case you need to find in which pool the buffer you try to recycle > belongs. In order to make the whole idea generic and be able to recycle skb > fragments instead of just the skb head you need to store some information on > struct page. That's the fundamental difference of this patchset compared to > the RFC we sent a few years back [1] which was just storing information on the > skb. The way this is done on the current patchset is that we store the > struct xdp_mem_info in page->private and then look it up on xdp_return(). > > Now that being said Matthew recently reworked struct page, so we could see if > we can store the page pool pointer directly instead of the struct > xdp_mem_info. That would allow us to call into page pool functions directly. > But we'll have to agree if that makes sense to go into struct page to begin > with and make sure the pointer is still valid when we take the recycling path. > Thinking more about it the reason that prevented us from storing a page pool pointer directly is not there anymore. Jesper fixed that already a while back. So we might as well store the page_pool ptr in page->private and call into the functions directly. I'll have a look before v4. [...] Thanks /Ilias
