On Thu, 2018-06-14 at 16:49 -0700, Eric Dumazet wrote: > > On 06/14/2018 02:04 PM, Saeed Mahameed wrote: > > > I was looking at the code without my fix :) > > > > with my fix: > > release = frags->page_offset + frag_info->frag_stride > PAGE_SIZE; > > > > for XDP: frag_info->frag_stride is PAGE_SIZE, so release will > > always be > > true regardless of PAGE_SIZE. > > > > So i guess i didn't quite understand your PowerPC concern.. can you > > elaborate ? > > > > So your maths with PAGE_SIZE=65536 and MTU 9000 > > frag_stride is about 9344 > > So if the last chunk of the page has 9100 bytes, we wont be able to > use it, while really we should be able to use it. > >
this is only true for XDP setup, for non XDP max stride_size can only be around ~3k and only for mtu > ~6k For XDP setup you suggested: - priv->frag_info[0].frag_size = eff_mtu; + priv->frag_info[0].frag_size = PAGE_SIZE; currently the condition is: release = frags->page_offset + frag_info->frag_size > PAGE_SIZE; so my solution and yours have the same problem you described above. the problem is not with the initial values or with stride/farg size math, it just that in XDP we shouldn't reuse at ALL. I agree with you that we need to optimize and maybe for PAGE_SIZE > 8k we need to allow XDP setup to reuses. but for now there is a data corruption to handle.
