I set up PiAware 3.8.1 on a Pi 4 with a UAT 978 Mhz and a 1090 Mhz Airnav Radarbox Flightstick about a week ago and everything has been working great.
Then a couple days ago, I installed timelapse1090, but I didn’t inspect its install script closely enough first and failed to notice that it forceable upgrades all installed packages on your system without asking your permission first (via apt-get upgrade -y). Among other changes, this caused my PiAware Linux kernel to be force upgraded from Linux version 4.19.118-v7l+ to Linux version 5.4.51-v7l+
Yesterday, after I rebooted my PiAware, I noticed that the CPU usage of dump1090-fa shot up from around 7% to around 40%:
which also caused the overall CPU load on my machine to increase from around 10% to around 16%:
along with a couple degree rise in overall core temperature.
The system seems to otherwise be operating fine and I am continuing to receive 1090 and 978 tracks at about the same rate I did before. The only difference I noticed was that both dump1090-fa and dump978-fa are no longer giving this warning on startup:
Detected Kernel usbfs mmap() bug, falling back to buffers in userspace
So I assume that this kernel usbfs bug was fixed in the Linux 5.4.51 kernel.
My questions:
- Would dump1090-fa switching to using kernel instead of userspace USB buffers explain its dramatic increase in CPU usage?
- Is there any advantage to using kernel buffers and if not, is there a way to force it to use buffers in userspace again to reduce the CPU load?
Thanks for any insights into this!