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Date:   Tue, 20 Mar 2018 10:28:01 +0800
From:   Jason Wang <>
To:     Jesper Dangaard Brouer <>
        BjörnTöpel <>,,,
        John Fastabend <>,
        Eran Ben Elisha <>,
        Saeed Mahameed <>,,
        Daniel Borkmann <>,
        Alexei Starovoitov <>,
        Tariq Toukan <>
Subject: Re: [bpf-next V3 PATCH 00/15] XDP redirect memory return API

On 2018年03月19日 18:10, Jesper Dangaard Brouer wrote:
> On Fri, 16 Mar 2018 17:04:17 +0800
> Jason Wang <> wrote:
>> Looks like the series forget to register memory model for tun and
>> virtio-net.
> Well, no.  It is actually not strictly necessary to invoke
> xdp_rxq_info_reg_mem_model() because enum MEM_TYPE_PAGE_SHARED == 0.
> And if not passing an allocator pointer to the call, then an mem_id is
> not registered... and __xdp_return_frame() skips the rhashtable_lookup.

I see.

> I designed the API this way, because I want to support later adding an
> allocator even for the refcnt scheme MEM_TYPE_PAGE_SHARED.  (As it
> would be a performance optimization to return the pages to the
> originating RX-CPU, and move the page refcnt dec back to that orig CPU).
> I did add an xdp_rxq_info_reg_mem_model() call to ixgbe, for human
> programmer "documentation" even-though it isn't strickly necessary.  I
> guess, I could add similar calls to tun and virtio_net, and then we
> avoid any implicit assumptions. And makes it more clear that
> XDP_REDIRECT support use the memory model return API.

Yes, please do it or add a comment somewhere.


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