From: Wander Lairson Costa > Sent: 16 March 2022 14:37 > > Note: I am using a small test app + driver located at [0] for the > problem description. serco is a driver whose write function dispatches > to the serial controller. sertest is a user-mode app that writes n bytes > to the serial console using the serco driver. > > While investigating a bug in the RHEL kernel, I noticed that the serial > console throughput is way below the configured speed of 115200 bps in > a HP Proliant DL380 Gen9. I was expecting something above 10KB/s, but > I got 2.5KB/s. > > $ time ./sertest -n 2500 /tmp/serco > > real 0m0.997s > user 0m0.000s > sys 0m0.997s > > With the help of the function tracer, I then noticed the serial > controller was taking around 410us seconds to dispatch one single byte: Did you verify the baud rate? Or is there some horrid serial redirection going on. It is even possible there is a bios smm interrupt chugging through on another cpu core. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
