USB Latency difference between RHEL and Fedora
Is there anything that can cause drastic latency differences in USB transfer speeds between RHEL 7.5 (3.10.0-862.14.4.el7.x86_64) and Fedora 26 (4.16.11-100.fc26.x86_64)?
My company physically connects an RS422 device, through RS422 to USB, using the FTDI_SIO driver. These devices send an ASCII string of characters to our software running on the linux machine.
We have a server that we have tested with 3 HDDs, each with a separate OS: RHEL 7.5 (server), RHEL 7.5 (Desktop), Fedora (23).
When our software & RS422 device runs on Fedora, the Latency is approx. 48-51 MS per transaction. When it runs on either RHEL OS, the latency is approx 2267 MS/transaction.
Outside of the OS, all other factors are identical. We are using the same physical server, the same RS422 devices, the same FTDI driver and the same software build to talk with the FTDI.
As of this morning (10/17/18), all Operating Systems are up to date and, and have the latest versions of usbutils, libusb, usbmuxd, usb_Modeswitch and USB-reder packages install.
Logically, it seems there is something different between the RHEL & Fedora builds (USB configuration setting, USB monitoring, etc) thats causing the difference in speed. However, I haven't been able to pin point anything yet.
