On Thu, 16 Feb 2017 14:36:41 -0800 John Fastabend <john.fastab...@gmail.com> wrote:
> On 17-02-16 12:41 PM, Alexander Duyck wrote: > > So I'm in the process of working on enabling XDP for the Intel NICs > > and I had a few questions so I just thought I would put them out here > > to try and get everything sorted before I paint myself into a corner. > > > > So my first question is why does the documentation mention 1 frame per > > page for XDP? Yes, XDP defines upfront a memory model where there is only one packet per page[1], please respect that! This is currently used/needed for fast-direct recycling of pages inside the driver for XDP_DROP and XDP_TX, _without_ performing any atomic refcnt operations on the page. E.g. see mlx4_en_rx_recycle(). This is also about controlling the cache-coherency state of the struct-page cache-line. (With two (or-more) packets per page, the struct-page cache-line will be jumping around.) Controlling this is essential when packets are transferred between CPUs. We need an architecture were we can control this, please. [1] https://prototype-kernel.readthedocs.io/en/latest/networking/XDP/design/requirements.html#page-per-packet -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
