netdev - Re: [RFC PATCH 4/5] mlx4: add support for fast rx drop bpf program

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Message-ID: <20160404165701.2a25a17a@redhat.com>
Date:	Mon, 4 Apr 2016 16:57:01 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Brenden Blanco <bblanco@...mgrid.com>, davem@...emloft.net,
	netdev@...r.kernel.org, tom@...bertland.com,
	Or Gerlitz <ogerlitz@...lanox.com>, daniel@...earbox.net,
	john.fastabend@...il.com, brouer@...hat.com
Subject: Re: [RFC PATCH 4/5] mlx4: add support for fast rx drop bpf program


On Fri, 1 Apr 2016 19:47:12 -0700 Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> My guess we're hitting 14.5Mpps limit for empty bpf program
> and for program that actually looks into the packet because we're
> hitting 10G phy limit of 40G nic. Since physically 40G nic
> consists of four 10G phys. There will be the same problem
> with 100G and 50G nics. Both will be hitting 25G phy limit.
> We need to vary packets somehow. Hopefully Or can explain that
> bit of hw design.
> Jesper's experiments with mlx4 showed the same 14.5Mpps limit
> when sender blasting the same packet over and over again.

That is an interesting observation Alexei, and could explain the pps limit
I hit on 40G, with single flow testing.  AFAIK 40G is 4x 10G PHYs, and
100G is 4x 25G PHYs.

I have a pktgen script that tried to avoid this pitfall.  By creating a
new flow per pktgen kthread. I call it "pktgen_sample05_flow_per_thread.sh"[1]

[1] https://github.com/netoptimizer/network-testing/blob/master/pktgen/pktgen_sample05_flow_per_thread.sh

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer