netdev - Re: [RFC PATCH net-next] net: pktgen: packet bursting via skb->xmit

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Date:	Fri, 26 Sep 2014 08:59:21 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH net-next] net: pktgen: packet bursting via skb->xmit_more

On Fri, Sep 26, 2014 at 8:44 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Fri, 2014-09-26 at 00:42 -0700, Eric Dumazet wrote:
>> On Thu, 2014-09-25 at 18:20 -0700, Eric Dumazet wrote:
>> > On Thu, 2014-09-25 at 17:46 -0700, Alexei Starovoitov wrote:
>> > > This patch demonstrates the effect of delaying update of HW tailptr.
>> > > (based on earlier patch by Jesper)
>> > >
>> > > burst=1 is a default. It sends one packet with xmit_more=false
>> > > burst=2 sends one packet with xmit_more=true and
>> > >         2nd copy of the same packet with xmit_more=false
>> > > burst=3 sends two copies of the same packet with xmit_more=true and
>> > >         3rd copy with xmit_more=false
>> >
>> > >
>> > > Cc: Jesper Dangaard Brouer <brouer@...hat.com>
>> > > Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
>> > > ---
>> >
>> > Perfect, this is what I had in mind, thanks !
>> >
>> > Acked-by: Eric Dumazet <edumazet@...gle.com>
>> >
>>
>> By the way with this patch, I now reach 10 Mpps on mlx4
>
> On the other hand, bnx2x is not that happy
>
> [  381.424736] bnx2x: [bnx2x_start_xmit:3772(eth0)]BUG! Tx ring full
> when queue awake!
> [  381.432660] bnx2x: [bnx2x_start_xmit:3772(eth0)]BUG! Tx ring full
> when queue awake!
> [  381.440337] bnx2x: [bnx2x_start_xmit:3772(eth0)]BUG! Tx ring full
> when queue awake!
> [  381.448255] bnx2x: [bnx2x_start_xmit:3772(eth0)]BUG! Tx ring full
> when queue awake!
>
> When TX_BUSY is replied, and/or  netif_tx_stop_queue(txq) was done by
> the driver, the 'burst' loop should stop
>
> So your :
>
>         if (more)
>                 goto xmit_more;
>
> Should instead be :
>
>         if (more && !netif_xmit_frozen_or_drv_stopped(txq))
>                 goto xmit_more;
>

oh. thanks for testing! That makes sense.
I don't think I can find bnx2x around to double check this.
Do you mind applying this fix and resubmitting with two sob?
This one was rfc anyway :)
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