netdev - Re: r8169: regression in connection speed with kernels 6.2+ (interrupt coalescing)

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Message-ID: <c1eb782d2fedbb0dbd2b249fac19faadf6c36857.camel@falix.de>
Date: Tue, 05 Nov 2024 20:57:49 +0100
From: Felix Braun <f.braun@...ix.de>
To: Heiner Kallweit <hkallweit1@...il.com>, nic_swsd@...ltek.com
Cc: netdev@...r.kernel.org
Subject: Re: r8169: regression in connection speed with kernels 6.2+
 (interrupt coalescing)


On 04.11.2024 14:57 +0100 Heiner Kallweit wrote:
> On 04.11.2024 13:47, Felix Braun wrote:
> > Nono, I mean 100MBytes/s ;-) My testcase is transferring a large file over
SMB and looking at the transfer speed as reported by KDE. (I'm attaching a full
dmsg of a boot of a 6.11.6 kernel with only irq_coalescing commented out
otherwise as released.)
> >
> 
> This test case involves several layers. To rule out conflicts on higher
levels:  
> Can you test with iperf to another machine in the same local network?

Measuring the performance with iperf3 I still see a difference in throughput by
a factor of 3:

WITH napi_defer_hard_irqs=0
===========================
[  5] local 2001:a61:11c6:9501:982a:b19f:94fc:71d1 port 41716 connected to
2001:a61:11c6:9501:97a8:b80a:4317:435e port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   112 MBytes   941 Mbits/sec    0    315 KBytes
[  5]   1.00-2.00   sec   110 MBytes   927 Mbits/sec    0    340 KBytes
[  5]   2.00-3.00   sec   111 MBytes   930 Mbits/sec    0    372 KBytes
[  5]   3.00-4.00   sec   111 MBytes   930 Mbits/sec    0    372 KBytes
[  5]   4.00-5.00   sec   110 MBytes   926 Mbits/sec    0    372 KBytes
[  5]   5.00-6.00   sec   111 MBytes   929 Mbits/sec    0    372 KBytes
[  5]   6.00-7.00   sec   110 MBytes   924 Mbits/sec    0    372 KBytes
[  5]   7.00-8.00   sec   111 MBytes   932 Mbits/sec    0    372 KBytes
[  5]   8.00-9.00   sec   110 MBytes   924 Mbits/sec    0    372 KBytes
[  5]   9.00-10.00  sec   111 MBytes   928 Mbits/sec    0    372 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.08 GBytes   929 Mbits/sec    0             sender
[  5]   0.00-10.00  sec  1.08 GBytes   928 Mbits/sec                  receiver

WITH napi_defer_hard_irqs=1
===========================
Connecting to host leporello, port 5201
[  5] local 2001:a61:11c6:9501:982a:b19f:94fc:71d1 port 42338 connected to
2001:a61:11c6:9501:97a8:b80a:4317:435e port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  37.0 MBytes   310 Mbits/sec    0    806 KBytes
[  5]   1.00-2.00   sec  35.0 MBytes   294 Mbits/sec    0    806 KBytes
[  5]   2.00-3.00   sec  35.1 MBytes   294 Mbits/sec    0    806 KBytes
[  5]   3.00-4.00   sec  35.0 MBytes   294 Mbits/sec    0    806 KBytes
[  5]   4.00-5.00   sec  35.2 MBytes   296 Mbits/sec    0    806 KBytes
[  5]   5.00-6.00   sec  35.0 MBytes   294 Mbits/sec    0    806 KBytes
[  5]   6.00-7.00   sec  34.9 MBytes   293 Mbits/sec    0    806 KBytes
[  5]   7.00-8.00   sec  34.9 MBytes   293 Mbits/sec    0    806 KBytes
[  5]   8.00-9.00   sec  35.0 MBytes   294 Mbits/sec    0    806 KBytes
[  5]   9.00-10.00  sec  35.2 MBytes   295 Mbits/sec    0    806 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   352 MBytes   296 Mbits/sec    0             sender
[  5]   0.00-10.02  sec   349 MBytes   292 Mbits/sec                  receiver


> Would be worth a try to see how system behaves with ASPM enabled in the
kernel.  
> Even though BIOS denies ASPM access for the kernel:  
> "can't disable ASPM; OS doesn't have ASPM control"

I noticed that I disabled ASPM in the BIOS. So far I've not been able to find a
BIOS setting that makes that warning go away.

If you think, that the current settings are the best default values for most
users, I'd defer your better knowledge of the hardware. At least I'm happy
because I can get my performance back by disabling IRQ coalescing on a vanilla
kernel.

Regards
Felix