Okay, I’ve just finished some pretty thorough testing of the QoS on my J3160-based IPFire. There is definitely a correlation with ksoftirqd and bandwidth. I artificially dropped bandwidths for Classes 203 (Web), and 210 (Default), then raised them in 25Mbps increments in between tests. I watched the top line in htop and picked out the highest cpu usage for ksoftirqd that showed, and recorded the average download speed reported by Waveform’s BufferBloat Test at:
Results:
QoS set to 25Mbps: download speed of 25Mbps measured at ~1% cpu usage on ksoftirqd
QoS set to 50Mbps: download speed of 48Mbps measured at ~5% cpu usage on ksoftirqd
Qos set to 75Mbps: download speed of 72Mbps measured at ~12% cpu usage on ksoftirqd
Qos set to 100Mbps: download speed of 95Mbps measured at 25% cpu usage on ksoftirqd
QoS set to 125Mbps: download speed of 116Mbps measured at 31% cpu usage on ksoftirqd
QoS set to 150Mbps: download speed of 133Mbps measured at 38% cpu usage on ksoftirqd
QoS set to 175Mbps: download speed of 150Mbps measure at 47% cpu usage on ksoftirqd
QoS set to 200Mbps: download speed of 158Mbps measured at 58% cpu usage on ksoftirqd
QoS set to 225Mbps: download speed of 161Mbps measured at 64% cpu usage on ksoftirqd
Qos set to 250Mbps: download speed of 166Mbps measured at 60% cpu usage on ksoftirqd
QoS set to 275Mbps: download speed of 177Mbps measured at 63% cpu usage on ksoftirqd
QoS set to 300Mbps: download speed of 191Mbps measured at 79% cpu usage on ksoftirqd.
Edit:
%bandwidth retained:
| Bandwidth | %bandwidth retained |
|---|---|
| 25 | 97% |
| 50 | 95% |
| 75 | 96% |
| 100 | 95% |
| 125 | 93% |
| 150 | 88% |
| 175 | 85% |
| 200 | 79% |
| 225 | 72% |
| 250 | 66% |
| 275 | 64% |
| 300 | 64% |