netdev - Re: [PATCH iwl-next] igb: Retrieve Tx timestamp directly from interrupt

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Message-ID: <cc538c62-87cd-472f-bcfa-7b92dbd90a25@intel.com>
Date: Tue, 19 Aug 2025 16:24:05 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Kurt Kanzenbach <kurt@...utronix.de>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>
CC: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Richard Cochran
	<richardcochran@...il.com>, Vinicius Costa Gomes <vinicius.gomes@...el.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	<intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH iwl-next] igb: Retrieve Tx timestamp directly from
 interrupt



On 8/14/2025 11:50 PM, Kurt Kanzenbach wrote:
> Retrieve Tx timestamp directly from interrupt handler.
> 
> The current implementation uses schedule_work() which is executed by the
> system work queue to retrieve Tx timestamps. This increases latency and can
> lead to timeouts in case of heavy system load.
> 
> Therefore, fetch the timestamp directly from the interrupt handler.
> 
> The work queue code stays for the Intel 82576. Tested on Intel i210.
> 

The change makes sense to me. All we really have to do in the interrupt
is read the timestamp register, and then report it to stack. Its much
better to do that work immediately if we don't need any locking or other
CPU intensive tasks here.

I can confirm that 82576 does not have the interrupt, it was introduced
in later hardware.

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>


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