linux-kernel - Re: Latency spikes on V6.15.1 Preempt RT and maybe related to intel? IGB

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Message-ID: <87plf27apk.fsf@jax.kurt.home>
Date: Tue, 17 Jun 2025 15:35:03 +0200
From: Kurt Kanzenbach <kurt@...utronix.de>
To: Marc Strämke <marc.straemke@...ropuls.de>, Sebastian
 Andrzej Siewior
 <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: Latency spikes on V6.15.1 Preempt RT and maybe related to
 intel? IGB

On Tue Jun 17 2025, Marc Strämke wrote:
> Hi Kurt,
> On 17.06.25 12:54, Kurt Kanzenbach wrote:
>>> You don't have to live with it. You could add a read after the writes in
>>> the loop (wrfl()). This should help.
>> Something like this, which was done for Intel e1000?
>>
>> https://lore.kernel.org/intel-wired-lan/20241219192743.4499-1-gerhard@engleder-embedded.com/
>>
>> Thanks,
>> Kurt
>
> This works wonders (Latency spike down to 120 us from 700) ! I will 
> prepare a patch and submit it to LKML.

Great :-)

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