From: Yunsheng Lin <linyunsheng@xxxxxxxxxx> Date: Fri, 3 Mar 2023 20:44:24 +0800 > On 2023/3/3 19:22, Alexander Lobakin wrote: >> From: Yunsheng Lin <linyunsheng@xxxxxxxxxx> >> Date: Thu, 2 Mar 2023 10:30:13 +0800 [...] >> And they are fixed :D >> No drivers currently which use Page Pool mix PP pages with non-PP. And > > The wireless adapter which use Page Pool *does* mix PP pages with > non-PP, see below discussion: > > https://lore.kernel.org/netdev/156f3e120bd0757133cb6bc11b76889637b5e0a6.camel@xxxxxxxxx/ Ah right, I remember that (also was fixed). Not that I think it is correct to mix them -- for my PoV, a driver shoule either give *all* its Rx buffers as PP-backed or not use PP at all. [...] >> As Jesper already pointed out, not having a quick way to check whether >> we have to check ::pp_magic at all can decrease performance. So it's >> rather a shortcut. > > When we are freeing a page by updating the _refcount, I think > we are already touching the cache of ::pp_magic. But no page freeing happens before checking for skb->pp_recycle, neither in skb_pp_recycle() (skb_free_head() etc.)[0] nor in skb_frag_unref()[1]. > > Anyway, I am not sure checking ::pp_magic is correct when a > page will be passing between different subsystem and back to > the network stack eventually, checking ::pp_magic may not be > correct if this happens. > > Another way is to use the bottom two bits in bv_page, see: > https://www.spinics.net/lists/netdev/msg874099.html > >> >>> >>>> >>>> /* Allow SKB to reuse area used by xdp_frame */ >>>> xdp_scrub_frame(xdpf); >>>> >> >> Thanks, >> Olek >> . >> [0] https://elixir.bootlin.com/linux/latest/source/net/core/skbuff.c#L808 [1] https://elixir.bootlin.com/linux/latest/source/include/linux/skbuff.h#L3385 Thanks, Olek
