netdev - Re: Possible Memory tracking bug with Intel ICE driver and jumbo frames

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Message-ID: <445d48a8-8e4e-4605-bad8-4a80707a1452@intel.com>
Date: Wed, 30 Apr 2025 14:40:26 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Christoph Petrausch <christoph.petrausch@...pl.com>
CC: <netdev@...r.kernel.org>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>
Subject: Re: Possible Memory tracking bug with Intel ICE driver and jumbo
 frames

On 4/30/25 11:16, Christoph Petrausch wrote:
> Sorry, my mail client fucked up the format of the commands how to 
> reproduce the issue. Here is a corrected version.
> 
> On 4/30/25 10:59, Christoph Petrausch wrote:
>>
>> We can't reproduce the problem on kernel 5.15, but have seen it on 
>> v5.17,v5,18 and v6.1, v6.2, v6.6.85, v6.8 and v6.15-rc4-42- 
>> gb6ea1680d0ac. I'm in the process of git bisecting to find the commit 
>> that introduced this broken behaviour.

Thank you for the report, the commands, and bisecting efforts!
We will also try to dig deeper on our own.
(side note: CCing IWL ML typically yields faster reply times)

>>
>> On kernel 5.15, jumbo frames are received normally after the memory 
>> pressure is gone.
>>
>>
>> To reproduce, we currently use 2 servers (server-rx, server-tx)with an 
>> Intel E810-XXV NIC. To generate network traffic, we run 2 iperf3 
>> processes with 100 threads each on the load generating server server-tx
>>
>> iperf3 -c server-rx -P 100 -t 3000 -p 5201
>> iperf3 -c server-rx -P 100 -t 3000 -p 5202
>>
>> On the receiving server server-rx, we setup two iperf3 servers:
>>
>> iperf3 -s -p 5201
>> iperf3 -s -p 5202
>>
>> To generate memory pressure, we start stress-ng on the server-rx:
>> stress-ng --vm 1000 --vm-bytes $(free -g -L | awk '{ print $8 }')G -- 
>> vm-keep --timeout 1200s
>>
>> This consumes all the currently free memory. As soon as the 
>> PFMemallocDrop counter increases, we stop stress-ng. Now we see plenty 
>> of free memory again, but the counter is still increasing and we have 
>> seen problems with new TCP sessions, as soon as their packet size is 
>> above 1500 bytes.

The faulty state perpetuates then forever? (say, at least few minutes)

>>
>> [1] https://github.com/intel/ethernet-linux-ice
>>
>> Best regards, Christoph Petrausch 
> 
>