netdev - Re: [PATCH] net: af_packet: Use hrtimer to do the retire operation

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Message-ID: <689750ec91ef7_2ad372294d8@willemb.c.googlers.com.notmuch>
Date: Sat, 09 Aug 2025 09:45:16 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Xin Zhao <jackzxcui1989@....com>, 
 willemdebruijn.kernel@...il.com, 
 edumazet@...gle.com, 
 ferenc@...es.dev
Cc: davem@...emloft.net, 
 kuba@...nel.org, 
 pabeni@...hat.com, 
 horms@...nel.org, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Xin Zhao <jackzxcui1989@....com>
Subject: Re: [PATCH] net: af_packet: Use hrtimer to do the retire operation

Xin Zhao wrote:
> In a system with high real-time requirements, the timeout mechanism of
> ordinary timers with jiffies granularity is insufficient to meet the
> demands for real-time performance. Meanwhile, the optimization of CPU
> usage with af_packet is quite significant. Use hrtimer instead of timer
> to help compensate for the shortcomings in real-time performance.
> In HZ=100 or HZ=250 system, the update of TP_STATUS_USER is not real-time
> enough, with fluctuations reaching over 8ms (on a system with HZ=250).
> This is unacceptable in some high real-time systems that require timely
> processing of network packets. By replacing it with hrtimer, if a timeout
> of 2ms is set, the update of TP_STATUS_USER can be stabilized to within
> 3 ms.
> 
> Signed-off-by: Xin Zhao <jackzxcui1989@....com>

This is a resubmit of the patch you yesterday [1]? While the
discussion on the original patch was ongoing too.

Net-next is also closed. See also see also
Documentation/process/maintainer-netdev.rst for the process.

I'll take a closer look later. Agreed in principle that it's
preferable to replace timer with hrtimer than to add a CONFIG to
select between them.

[1] https://lore.kernel.org/netdev/20250808032623.11485-1-jackzxcui1989@163.com/