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From: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Date: Wed, 7 Feb 2024 16:55:17 +0500
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Subject: =?UTF-8?Q?Re=3A_This_is_the_fourth_time_I=E2=80=99ve_tried_to_find_wha?=
	=?UTF-8?Q?t_led_to_the_regression_of_outgoing_network_speed_and_each_t?=
	=?UTF-8?Q?ime_I_find_the_merge_commit_8c94ccc7cd691472461448f98e2372c7?=
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To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: "Christian A. Ehrhardt" <lk@c--e.de>, niklas.neronin@linux.intel.com, 
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>, Greg KH <gregkh@linuxfoundation.org>, 
	linux-usb@vger.kernel.org
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On Wed, Feb 7, 2024 at 3:39=E2=80=AFPM Mathias Nyman
<mathias.nyman@linux.intel.com> wrote:
>
> Thanks,
>
> Looks like your network adapter ends up interrupting CPU0 in the bad case=
 due
> to the change in how many interrupts are requested by xhci_hcd before it.
>
> bad case:
>         CPU0    CPU1    ...     CPU31
> 87:     18213809 0      ...     0       IR-PCI-MSIX-0000:0e:00.0    0-edg=
e      enp14s0
>
> Does manually changing it to some other CPU help? picking one that doesn'=
t already
> handle a lot of interrupts. CPU0 could also in general be more busy, poss=
ibly spending
> more time with interrupts disabled.
>
> For example change to CPU23 in the bad case:
>
> echo 800000 > /proc/irq/87/smp_affinity
>
> Check from proc/interrupts that enp14s0 interrupts actually go to CPU23 a=
fter this.
>
> Thanks
> Mathias
>

root@secondary-ws ~# iperf3 -c primary-ws.local -t 5 -p 5000 -P 1
Connecting to host primary-ws.local, port 5000
[  5] local 192.168.1.130 port 49152 connected to 192.168.1.96 port 5000
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  70.9 MBytes   594 Mbits/sec    0    376 KBytes
[  5]   1.00-2.00   sec  72.4 MBytes   607 Mbits/sec    0    431 KBytes
[  5]   2.00-3.00   sec  73.1 MBytes   613 Mbits/sec    0    479 KBytes
[  5]   3.00-4.00   sec  72.4 MBytes   607 Mbits/sec    0    501 KBytes
[  5]   4.00-5.00   sec  73.2 MBytes   614 Mbits/sec    0    501 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-5.00   sec   362 MBytes   607 Mbits/sec    0             sende=
r
[  5]   0.00-5.00   sec   360 MBytes   603 Mbits/sec                  recei=
ver

iperf Done.
root@secondary-ws ~# echo 800000 > /proc/irq/87/smp_affinity
root@secondary-ws ~# iperf3 -c primary-ws.local -t 5 -p 5000 -P 1
Connecting to host primary-ws.local, port 5000
[  5] local 192.168.1.130 port 37620 connected to 192.168.1.96 port 5000
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   111 MBytes   934 Mbits/sec    0    621 KBytes
[  5]   1.00-2.00   sec   109 MBytes   913 Mbits/sec    0    621 KBytes
[  5]   2.00-3.00   sec   110 MBytes   920 Mbits/sec    0    621 KBytes
[  5]   3.00-4.00   sec   110 MBytes   924 Mbits/sec    0    621 KBytes
[  5]   4.00-5.00   sec   109 MBytes   917 Mbits/sec    0    621 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-5.00   sec   549 MBytes   921 Mbits/sec    0             sende=
r
[  5]   0.00-5.00   sec   547 MBytes   916 Mbits/sec                  recei=
ver

iperf Done.

Very interesting, is CPU0 slower than CPU23 by 30%?

--=20
Best Regards,
Mike Gavrilov.