linux-kernel - Re: [PATCH net-next 1/1] net: stmmac: enhance XDP ZC driver level switching performance

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Date:   Sun, 14 Nov 2021 16:11:41 +0100
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Ong Boon Leong <boon.leong.ong@...el.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        alexandre.torgue@...s.st.com,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>
Cc:     netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Ong Boon Leong <boon.leong.ong@...el.com>
Subject: Re: [PATCH net-next 1/1] net: stmmac: enhance XDP ZC driver level
 switching performance

On Thu Nov 11 2021, Ong Boon Leong wrote:
> The previous stmmac_xdp_set_prog() implementation uses stmmac_release()
> and stmmac_open() which tear down the PHY device and causes undesirable
> autonegotiation which causes a delay whenever AFXDP ZC is setup.
>
> This patch introduces two new functions that just sufficiently tear
> down DMA descriptors, buffer, NAPI process, and IRQs and reestablish
> them accordingly in both stmmac_xdp_release() and stammac_xdp_open().
>
> As the results of this enhancement, we get rid of transient state
> introduced by the link auto-negotiation:
>
> $ ./xdpsock -i eth0 -t -z
>
>  sock0@...0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 634444         634560
>
>  sock0@...0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 632330         1267072
>
>  sock0@...0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 632438         1899584
>
>  sock0@...0:0 txonly xdp-drv
>                    pps            pkts           1.00
> rx                 0              0
> tx                 632502         2532160
>
> Reported-by: Kurt Kanzenbach <kurt@...utronix.de>
> Signed-off-by: Ong Boon Leong <boon.leong.ong@...el.com>

Tested-by: Kurt Kanzenbach <kurt@...utronix.de>

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