linux-kernel - Re: [PATCH net-next 14/15 v2] net: Reference bpf_redirect_info via task_struct on PREEMPT

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Date: Tue, 14 May 2024 07:07:21 +0200
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
 Toke Høiland-Jørgensen <toke@...hat.com>,
 LKML <linux-kernel@...r.kernel.org>,
 Network Development <netdev@...r.kernel.org>,
 "David S. Miller" <davem@...emloft.net>, Boqun Feng <boqun.feng@...il.com>,
 Daniel Borkmann <daniel@...earbox.net>, Eric Dumazet <edumazet@...gle.com>,
 Frederic Weisbecker <frederic@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>,
 Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>,
 Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Eduard Zingerman <eddyz87@...il.com>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, John Fastabend <john.fastabend@...il.com>,
 KP Singh <kpsingh@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>,
 Song Liu <song@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
 Yonghong Song <yonghong.song@...ux.dev>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH net-next 14/15 v2] net: Reference bpf_redirect_info via
 task_struct on PREEMPT_RT.

On 10/05/2024 18.22, Sebastian Andrzej Siewior wrote:
> On 2024-05-10 18:21:24 [+0200], To Jesper Dangaard Brouer wrote:
>> The XDP redirect process is two staged:
> …
> On 2024-05-07 15:27:44 [+0200], Jesper Dangaard Brouer wrote:
>>
>> I need/want to echo Toke's request to benchmark these changes.
> 
> I have:
> boxA: ixgbe
> boxB: i40e
> 
> Both are bigger NUMA boxes. I have to patch ixgbe to ignore the 64CPU
> limit and I boot box with only 64CPUs. The IOMMU has been disabled on
> both box as well as CPU mitigations. The link is 10G.
> 
> The base for testing I have is commit a17ef9e6c2c1c ("net_sched:
> sch_sfq: annotate data-races around q->perturb_period") which I used to
> rebase my series on top of.
> 
> pktgen_sample03_burst_single_flow.sh has been used to send packets and
> "xdp-bench drop $nic -e" to receive them.
> 

Sorry, but a XDP_DROP test will not activate the code you are modifying.
Thus, this test is invalid and doesn't tell us anything about your code 
changes.

The code is modifying the XDP_REDIRECT handling system. Thus, the
benchmark test needs to activate this code.

> baseline
> ~~~~~~~~
> boxB -> boxA | gov performance
> -t2 (to pktgen)
> | receive total 14,854,233 pkt/s        14,854,233 drop/s                0 error/s
> 
> -t1 (to pktgen)
> | receive total 10,642,895 pkt/s        10,642,895 drop/s                0 error/s
> 
> 
> boxB -> boxA | gov powersave
> -t2 (to pktgen)
>    receive total 10,196,085 pkt/s        10,196,085 drop/s                0 error/s
>    receive total 10,187,254 pkt/s        10,187,254 drop/s                0 error/s
>    receive total 10,553,298 pkt/s        10,553,298 drop/s                0 error/s
> 
> -t1
>    receive total 10,427,732 pkt/s        10,427,732 drop/s                0 error/s
> 
> ======
> boxA -> boxB (-t1) gov performance
> performace:
>    receive total 13,171,962 pkt/s        13,171,962 drop/s                0 error/s
>    receive total 13,368,344 pkt/s        13,368,344 drop/s                0 error/s
> 
> powersave:
>    receive total 13,343,136 pkt/s        13,343,136 drop/s                0 error/s
>    receive total 13,220,326 pkt/s        13,220,326 drop/s                0 error/s
> 
> (I the CPU governor had no impact, just noise)
> 
> The series applied (with updated 14/15)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> boxB -> boxA | gov performance
> -t2:
>    receive total  14,880,199 pkt/s        14,880,199 drop/s                0 error/s
> 
> -t1:
>    receive total  10,769,082 pkt/s        10,769,082 drop/s                0 error/s
> 
> boxB -> boxA | gov powersave
> -t2:
>   receive total   11,163,323 pkt/s        11,163,323 drop/s                0 error/s
> 
> -t1:
>   receive total   10,756,515 pkt/s        10,756,515 drop/s                0 error/s
> 
> boxA -> boxB | gov perfomance
> 
>   receive total  13,395,919 pkt/s        13,395,919 drop/s                0 error/s
> 
> boxA -> boxB | gov perfomance
>   receive total  13,290,527 pkt/s        13,290,527 drop/s                0 error/s
> 
> 
> Based on my numbers, there is just noise.  BoxA hit the CPU limit during
> receive while lowering the CPU-freq. BoxB seems to be unaffected by
> lowing CPU frequency during receive.
> 
> I can't comment on anything >10G due to HW limits.
> 
> Sebastian