netdev - Re: [PATCH RFC net-next 1/2] net: Reference bpf_redirect_info via task_struct on PREEMPT

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Message-ID: <0b1c8247-ccfb-4228-bd64-53583329aaa7@kernel.org>
Date: Tue, 20 Feb 2024 11:42:57 +0100
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Toke Høiland-Jørgensen <toke@...hat.com>,
 bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC net-next 1/2] net: Reference bpf_redirect_info via
 task_struct on PREEMPT_RT.



On 20/02/2024 11.17, Sebastian Andrzej Siewior wrote:
> On 2024-02-20 10:17:53 [+0100], Jesper Dangaard Brouer wrote:
>>
>>
>> On 19/02/2024 20.01, Toke Høiland-Jørgensen wrote:
>>> may be simpler to use pktgen, and at 10G rates that shouldn't become a
>>> bottleneck either. The pktgen_sample03_burst_single_flow.sh script in
>>> samples/pktgen in the kernel source tree is fine for this usage.
>>
>> Example of running script:
>>   ./pktgen_sample03_burst_single_flow.sh -vi mlx5p1 -d 198.18.1.1 -m
>> ec:0d:9a:db:11:c4 -t 12
>>
>> Notice the last parameter, which is number threads to start.
>> If you have a ixgbe NIC driver, then I recommend -t 2 even if you have more
>> CPUs.
> 
> I get
> | Summary                 8,435,690 rx/s                  0 err/s

This seems low...
Have you remembered to disable Ethernet flow-control?

  # ethtool -A ixgbe1 rx off tx off
  # ethtool -A i40e2 rx off tx off


> | Summary                 8,436,294 rx/s                  0 err/s

You want to see the "extended" info via cmdline (or Ctrl+\)

  # xdp-bench drop -e eth1


> 
> with "-t 8 -b 64". I started with 2 and then increased until rx/s was
> falling again. I have ixgbe on the sending side and i40e on the

With ixgbe on the sending side, my testlab shows I need -t 2.

With -t 2 :
Summary                14,678,170 rx/s                  0 err/s
   receive total        14,678,170 pkt/s        14,678,170 drop/s 
         0 error/s
     cpu:1              14,678,170 pkt/s        14,678,170 drop/s 
         0 error/s
   xdp_exception                 0 hit/s

with -t 4:

Summary                10,255,385 rx/s                  0 err/s
   receive total        10,255,385 pkt/s        10,255,385 drop/s 
         0 error/s
     cpu:1              10,255,385 pkt/s        10,255,385 drop/s 
         0 error/s
   xdp_exception                 0 hit/s

> receiving side. I tried to receive on ixgbe but this ended with -ENOMEM
> | # xdp-bench drop eth1
> | Failed to attach XDP program: Cannot allocate memory
> 
> This is v6.8-rc5 on both sides. Let me see where this is coming from…
> 

Another pitfall with ixgbe is that it does a full link reset when
adding/removing XDP prog on device.  This can be annoying if connected
back-to-back, because "remote" pktgen will stop on link reset.

--Jesper