Messages in this thread | | | Date | Fri, 1 Apr 2022 12:07:05 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v5 1/1] serial/8250: Use fifo in 8250 console driver |
| |
On Fri, 1 Apr 2022 06:35:58 +0200 Jiri Slaby <jirislaby@kernel.org> 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
| |