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Ethernet performance degradation on power save mode

Guru 20755 points


Hello,

I have degredation in ethernet performance when I use power mode features in kernel.

I see that I get degregation when there is no activity in serial (from time of starting the test till finishing the test). I thought That it means that cpu gets into retention in such scenario, but to my surprise the retention counter did not change during the test:

~ # cat /sys/devices/system/cpu/cpu0/cpuidle/state4/time
70254200

~ # ./iperf -c 150.42.40.220 -w 2000
WARNING: TCP window size set to 2000 bytes. A small window size
will give poor performance. See the Iperf documentation.
------------------------------------------------------------
Client connecting to 150.42.40.220, TCP port 5001
TCP window size: 3.91 KByte (WARNING: requested 1.95 KByte)
------------------------------------------------------------
[ 5] local 150.42.40.221 port 49380 connected with 150.42.40.220 port 5001
[ ID] Interval Transfer Bandwidth
[ 5] 0.0-10.0 sec 7.67 MBytes 6.43 Mbits/sec

~ # cat /sys/devices/system/cpu/cpu0/cpuidle/state4/time
70254200


What can be the reason for this degredation ?
When I set in code sleep_while_idle = 0.I have no degredation (though there is no entering into retention at all). Is it that there is some failure in the counter progress that can explain this ?


Regards,
Ran