On Wed, Feb 28, 2024 at 07:05:56PM +0800, Yunjian Wang wrote:
> This patch set allows TUN to support the AF_XDP Tx zero-copy feature,
> which can significantly reduce CPU utilization for XDP programs.
Why no Rx ZC support though? What will happen if I try rxdrop xdpsock
against tun with this patch? You clearly allow for that.
>
> Since commit fc72d1d54dd9 ("tuntap: XDP transmission"), the pointer
> ring has been utilized to queue different types of pointers by encoding
> the type into the lower bits. Therefore, we introduce a new flag,
> TUN_XDP_DESC_FLAG(0x2UL), which allows us to enqueue XDP descriptors
> and differentiate them from XDP buffers and sk_buffs. Additionally, a
> spin lock is added for enabling and disabling operations on the xsk pool.
>
> The performance testing was performed on a Intel E5-2620 2.40GHz machine.
> Traffic were generated/send through TUN(testpmd txonly with AF_XDP)
> to VM (testpmd rxonly in guest).
>
> +------+---------+---------+---------+
> | | copy |zero-copy| speedup |
> +------+---------+---------+---------+
> | UDP | Mpps | Mpps | % |
> | 64 | 2.5 | 4.0 | 60% |
> | 512 | 2.1 | 3.6 | 71% |
> | 1024 | 1.9 | 3.3 | 73% |
> +------+---------+---------+---------+
>
> Signed-off-by: Yunjian Wang <wangyunjian@xxxxxxxxxx>
> ---
> drivers/net/tun.c | 177 +++++++++++++++++++++++++++++++++++++++--
> drivers/vhost/net.c | 4 +
> include/linux/if_tun.h | 32 ++++++++
> 3 files changed, 208 insertions(+), 5 deletions(-)
>
