I am executing a timing-critical application on my ApalisT30/Ixora system that reads data from a device via usb serial on the mini-PCIe interface. I’m running into kernel messages telling me that my tty device is getting input overruns, e.g.:
[77336.971830] ttyUSB0: 1 input overrun(s)
[77338.011834] ttyUSB0: 1 input overrun(s)
[77339.973829] ttyUSB0: 1 input overrun(s)
The application has to do quite a bit of logging, and it occurred to me that I might be experiencing an I/O bottleneck, specifically slow writes to rootfs on eMMC. To test that theory, I created a tmpfs ramdisk and redirected logging to that device, but still have the overruns.
It very well may be program logic, but I’d like to eliminate the possibility of an I/O bottleneck, so I wanted to verify performance (i.e. bandwidth) of eMMC, DDR and confirm that tmpfs is staged in DDR and not eMMC.