Changing CPU indicator from Powersave to Performance did not improve ping results

Shayne

10/20/23, 11:31 AM

I am trying to ping between two PCs running Ubuntu 20.04 connected via a Layer-2 switch. My goal is to get "nearly" stable ping latency. Similar to other people, I figured out that ping latency (round-trip-time) under a low CPU load gets worse than under a higher CPU load.

https://superuser.com/questions/543503/ping-vs-cpu-usage

https://superuser.com/questions/1189531/kvm-how-is-cpu-usage-related-to-ping

For instance, let say I am pinging from PC-A to PC-B. When PC-B did not run any program other than default programs in the operating system, the ping latency received on PC-A was around 0.5 - 0.6 ms. However, when I used the stress tool to increase CPU load (e.g., stress one core to 80% load), I saw that the ping latency received on PC-A was just around 0.2 - 0.3 ms.

I am sure the problem is not caused by the switch because I also tried the direct cable between PC-A and PC-B and still got the same behavior. I am pretty sure that this behavior is caused by powersave mode, which is the default CPU indicator. But what surprises me is that when I changed CPU indicator from powersave mode to performance mode using cpufrequtils, the ping latency received on PC-A was still around 0.5 - 0.6 ms (no load on PC-B). The same behavior (the ping latency around 0.2 - 0.3 ms) happened when I increased CPU load. In addition to changing the CPU indicator, I guess I still need to do something else.

0 + 0

networking

power-management

cpufreq

cpu

20.04

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Changing CPU indicator from Powersave to Performance did not improve ping results

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.