netdev - Re: [PATCH net-next 1/2] virtio-net: correctly update XDP

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Date:   Wed, 1 Aug 2018 09:31:48 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] virtio-net: correctly update XDP_TX counters



On 2018年07月31日 17:57, Toshiaki Makita wrote:
> On 2018/07/31 18:43, Jason Wang wrote:
>> Commit 5b8f3c8d30a6 ("virtio_net: Add XDP related stats") tries to
>> count TX XDP stats in virtnet_receive(). This will cause several
>> issues:
>>
>> - virtnet_xdp_sq() was called without checking whether or not XDP is
>>    set. This may cause out of bound access when there's no enough txq
>>    for XDP.
>> - Stats were updated even if there's no XDP/XDP_TX.>
>> Fixing this by reusing virtnet_xdp_xmit() for XDP_TX which can counts
>> TX XDP counter itself and remove the unnecessary tx stats embedded in
>> rx stats.
> Thanks for fixing this.
> I wanted to avoid calling u64_stats_update_begin() (i.e. smp_wmb() in 32
> bit systems) for every packet. So I'd like to keep sq stats in
> virtnet_rx_stats.
>

We can optimize this by adding batching on top. (virtnet_xdp_xmit() 
accepts an array of xdp frames). If you like, please send a patch for this.

Thanks