linux – Unstable TCP_STREAM Throughput with Netperf on Raspberry Pi – High Send-Q Values

I’m using Netperf on a Raspberry Pi to send TCP_STREAM data to a server with a message size of 1024 bytes. However, I’m experiencing irregular throughput, where it fluctuates between high and low values.
Upon investigating, I observed the following behavior using ss -i:

When the throughput is high, the send-q values are also high.

When the throughput drops, the send-q values decrease significantly.

I’m trying to understand why this is happening. What could be causing the send-q values to spike during periods of high throughput and drop when the throughput decreases? Any insights or troubleshooting tips would be greatly appreciated.