netdev - Re: [PATCH v2 net-next] mlx4: optimize xmit path

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Date:	Thu, 2 Oct 2014 11:03:13 +0300
From:	Amir Vadai <amirv@...lanox.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	Or Gerlitz <gerlitz.or@...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>,
	Or Gerlitz <or.gerlitz@...il.com>, <amira@...lanox.com>,
	<idos@...lanox.com>, "Yevgeny Petrilin" <yevgenyp@...lanox.com>,
	<eyalpe@...lanox.com>
Subject: Re: [PATCH v2 net-next] mlx4: optimize xmit path

On 10/2/2014 7:35 AM, Eric Dumazet wrote:
> On Sun, 2014-09-28 at 21:19 -0700, Eric Dumazet wrote:
>> From: Eric Dumazet <edumazet@...gle.com>
> 

[...]

> Sorry, there is a missing replacement of 
> 
> 	iowrite32be(ring->doorbell_qpn,
> 		    ring->bf.uar->map + MLX4_SEND_DOORBELL);
> 
> by iowrite32(ring->doorbell_qpn,
> 	     ring->bf.uar->map + MLX4_SEND_DOORBELL);
> 
> Since doorbel_qpn was changed to a __be32 and setup in
> mlx4_en_activate_tx_ring()
> 

Hi,

Will take it into the split patchset - we just hit this bug when tried
to run benchmarks with blueflame disabled (easy to test by using ethtool
priv flag blueflame).

I'm still working on it, but I can't reproduce the numbers that you
show. On my development machine, I get ~5.5Mpps with burst=8 and ~2Mpps
with burst=1.

In addition, I see no improvements when adding the optimization to the
xmit path.
I use the net-next kernel + pktgen burst support patch, with and without
this xmit path optimization patch.

Do you use other patches not upstream in your environment?
Can you share the .config/pktgen configuration?

One other note: we're checking now that blueflame could be used with
xmit_more. It might result with packets reordering/drops. Still under
investigation.

Thanks,
Amir
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