On Fri, 1 Apr 2022 06:35:58 +0200 Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: > > With the help of the function tracer, I then noticed the serial > > controller was taking around 410us seconds to dispatch one single byte: > > > > $ trace-cmd record -p function_graph -g serial8250_console_write \ > > ./sertest -n 1 /tmp/serco > > > > $ trace-cmd report > > Note, the function graph tracer can add a noticeable amount of overhead to these timings. If you want a more accurate time for a function, just trace that one function: trace-cmd record -p function_graph -l serial8250_console_write ... As that will only trace the serial8250_console_write() function (think of -l as "limit"), and the overhead of function graph for tracing a single function becomes negligible, and then you can see the true time of that function. -- Steve
