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

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Message-ID: <aKcYFbzbbfPXlrlN@localhost>
Date: Thu, 21 Aug 2025 14:59:01 +0200
From: Miroslav Lichvar <mlichvar@...hat.com>
To: Kurt Kanzenbach <kurt@...utronix.de>
Cc: Jacob Keller <jacob.e.keller@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	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: [Intel-wired-lan] [PATCH iwl-next] igb: Retrieve Tx timestamp
 directly from interrupt

On Thu, Aug 21, 2025 at 01:38:44PM +0200, Kurt Kanzenbach wrote:
> On Wed Aug 20 2025, Jacob Keller wrote:
> > On 8/20/2025 12:56 AM, Miroslav Lichvar wrote:
> >> But when I increase the rate to 200000, I get this:
> >> 
> >> Without the patch:
> >> NTP daemon TX timestamps   : 35835
> >> NTP kernel TX timestamps   : 1410956
> >> NTP hardware TX timestamps : 581575            
> >> 
> >> With the patch:
> >> NTP daemon TX timestamps   : 476908
> >> NTP kernel TX timestamps   : 646146
> >> NTP hardware TX timestamps : 412095

> Miroslav, can you test the following patch? Does this help?

It seems better than with the original patch, but not as good as
before, at least in the tests I'm doing. The maximum packet rate the
server can handle is now only about 5% worse (instead of 40%), but the
the number of missing timestamps on the server still seems high.

With the new patch at 200000 requests per second:
NTP daemon TX timestamps   : 192404
NTP kernel TX timestamps   : 1318971
NTP hardware TX timestamps : 418805

I didn't try to adjust the aux worker priority.

-- 
Miroslav Lichvar