Subject: Re: [PATCH v2 net-next] net: fec: Enable SOC specific rx-usecs coalescence default setting

From: Jakub Kicinski <[email-masked]>
Date: Fri, 26 Jul 2024 19:38:03 -0700

On Fri, 26 Jul 2024 09:53:12 -0500 Shenwei Wang wrote:
> The current FEC driver uses a single default rx-usecs coalescence setting
> across all SoCs. This approach leads to suboptimal latency on newer, high
> performance SoCs such as i.MX8QM and i.MX8M.
> 
> For example, the following are the ping result on a i.MX8QXP board:
> 
> $ ping 192.168.0.195
> PING 192.168.0.195 (192.168.0.195) 56(84) bytes of data.
> 64 bytes from 192.168.0.195: icmp_seq=1 ttl=64 time=1.32 ms
> 64 bytes from 192.168.0.195: icmp_seq=2 ttl=64 time=1.31 ms
> 64 bytes from 192.168.0.195: icmp_seq=3 ttl=64 time=1.33 ms
> 64 bytes from 192.168.0.195: icmp_seq=4 ttl=64 time=1.33 ms
> 
> The current default rx-usecs value of 1000us was originally optimized for
> CPU-bound systems like i.MX2x and i.MX6x. However, for i.MX8 and later
> generations, CPU performance is no longer a limiting factor. Consequently,
> the rx-usecs value should be reduced to enhance receive latency.
> 
> The following are the ping result with the 100us setting:
> 
> $ ping 192.168.0.195
> PING 192.168.0.195 (192.168.0.195) 56(84) bytes of data.
> 64 bytes from 192.168.0.195: icmp_seq=1 ttl=64 time=0.554 ms
> 64 bytes from 192.168.0.195: icmp_seq=2 ttl=64 time=0.499 ms
> 64 bytes from 192.168.0.195: icmp_seq=3 ttl=64 time=0.502 ms
> 64 bytes from 192.168.0.195: icmp_seq=4 ttl=64 time=0.486 ms
> 
> Performance testing using iperf revealed no noticeable impact on
> network throughput or CPU utilization.

Sounds like an optimization, net-next is still closed:
https://netdev.bots.linux.dev/net-next.html
Please repost after Monday.
-- 
pw-bot: defer