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

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Date:	Sat, 27 Sep 2014 23:55:52 +0300
From:	Or Gerlitz <gerlitz.or@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Amir Vadai <amirv@...lanox.com>,
	Or Gerlitz <or.gerlitz@...il.com>
Subject: Re: [RFC PATCH net-next] net: pktgen: packet bursting via skb->xmit_more

On Sat, Sep 27, 2014 at 11:43 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Fri, 2014-09-26 at 00:42 -0700, Eric Dumazet wrote:
>
>> By the way with this patch, I now reach 10 Mpps on mlx4
>>
>> base line : 5 Mpps
>>
>> + skb->xmit_more and quick hack in pjtgen (spinlock/unlock per packet)
>> -> 7 Mpps
>>
>> + burst of 16 packets, no spinlock per packet -> 10 Mpps
>
> With careful study of mlx4 driver to remove false sharing, I now get 14
> Mpps.
>
> (Note they have a special feature to 'inline' small packets in tx
> descriptors : If this is used, max rate is lower, because cpu spend more
> cycles to perform the copies)
>
> I find worrying driver authors do not know how to properly use a ring
> buffer, and do not place the producer and consumer indexes in separate
> cache lines.

mmm, so the numberz sound good, the comment sounds as the basics are
still not fully behind us (so we have where to improve)... any mlx4
patch you want to share?
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