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From:   =?UTF-8?B?6buE5p2w?= <huangjie.albert@bytedance.com>
Date:   Mon, 20 Nov 2023 18:02:47 +0800
Message-ID: <CABKxMyPNYS=6BHhaMDOSSMu8F0C5jkoa5Tck1dE6QnLa6--6UQ@mail.gmail.com>
Subject: Re: [External] Re: [PATCH net] veth: fix ethtool statistical errors
To:     Lorenzo Bianconi <lorenzo@kernel.org>
Cc:     Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Toshiaki Makita <toshiaki.makita1@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Lorenzo Bianconi <lorenzo@kernel.org> =E4=BA=8E2023=E5=B9=B411=E6=9C=8820=
=E6=97=A5=E5=91=A8=E4=B8=80 17:52=E5=86=99=E9=81=93=EF=BC=9A
>
> > Lorenzo Bianconi <lorenzo@kernel.org> =E4=BA=8E2023=E5=B9=B411=E6=9C=88=
17=E6=97=A5=E5=91=A8=E4=BA=94 17:26=E5=86=99=E9=81=93=EF=BC=9A
> > >
> > > > if peer->real_num_rx_queues > 1, the ethtool -s command for
> > > > veth network device will display some error statistical values.
> > > > The value of tx_idx is reset with each iteration, so even if
> > > > peer->real_num_rx_queues is greater than 1, the value of tx_idx
> > > > will remain constant. This results in incorrect statistical values.
> > > > To fix this issue, assign the value of pp_idx to tx_idx.
> > > >
> > > > Fixes: 5fe6e56776ba ("veth: rely on peer veth_rq for ndo_xdp_xmit a=
ccounting")
> > > > Signed-off-by: Albert Huang <huangjie.albert@bytedance.com>
> > > > ---
> > > >  drivers/net/veth.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > > > index 0deefd1573cf..3a8e3fc5eeb5 100644
> > > > --- a/drivers/net/veth.c
> > > > +++ b/drivers/net/veth.c
> > > > @@ -225,7 +225,7 @@ static void veth_get_ethtool_stats(struct net_d=
evice *dev,
> > > >       for (i =3D 0; i < peer->real_num_rx_queues; i++) {
> > > >               const struct veth_rq_stats *rq_stats =3D &rcv_priv->r=
q[i].stats;
> > > >               const void *base =3D (void *)&rq_stats->vs;
> > > > -             unsigned int start, tx_idx =3D idx;
> > > > +             unsigned int start, tx_idx =3D pp_idx;
> > > >               size_t offset;
> > > >
> > > >               tx_idx +=3D (i % dev->real_num_tx_queues) * VETH_TQ_S=
TATS_LEN;
> > > > --
> > > > 2.20.1
> > > >
> > >
> > > Hi Albert,
> > >
> > > Can you please provide more details about the issue you are facing?
> > > In particular, what is the number of configured tx and rx queues for =
both
> > > peers?
> >
> > Hi, Lorenzo
> > I found this because I wanted to add more echo information in ethttool=
=EF=BC=88for veth,
> > but I found that the information was incorrect. That's why I paid
> > attention here.
>
> ack. Could you please share the veth pair tx/rx queue configuration?
>

dev: tx --->4.  rx--->4
peer: tx--->1 rx---->1

Could the following code still be problematic? pp_idx not updated correctly=
.
page_pool_stats:
veth_get_page_pool_stats(dev, &data[pp_idx]);

BR
Albert

> Rergards,
> Lorenzo
>
> >
> > > tx_idx is the index of the current (local) tx queue and it must resta=
rt from
> > > idx in each iteration otherwise we will have an issue when
> > > peer->real_num_rx_queues is greater than dev->real_num_tx_queues.
> > >
> > OK. I don't know if this is a known issue.
> >
> > BR
> > Albert
> >
> >
> > > Regards,
> > > Lorenzo