Messages in this thread | | | From | Peter Chen <> | Subject | RE: [PATCH v1 2/2] usb:cdns3 Add Cadence USB3 DRD Driver | Date | Thu, 13 Dec 2018 01:21:29 +0000 |
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> > > > Felipe, I use Dynamic Debug for debugging, and show debug messages > > with "dmesg" after testing/debugging. I see dwc3 using trace, any > > benefits for switching to trace? > > The benefits I see are >
Thanks, bin.
> - *by default*, the debug log doesn't have to go through uart console, > which is slow. > > I typically 'cat trace_pipe' from a telnet which is much faster then > uart. But Dynamic Debug log by default got printed on uart, I have to > set printk level to not print them, which is an extra step. >
It depends on the rootfs's setting. By default, the debug message level should be off ( console level = 7)
> - tracepoint uses one place to decode the message vs DD has to repeat > the similar print statement in the code; and tracepoint decodes it > offline which reduce the kernel runtime overhead too. >
offline? You mean when you run "cat trace_pipe"?
> - with tracepoint, it is easier to turn on debug for a specific group of > messages. >
The DD can, but we don't do it often.
https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html?highlight=dynamic%20debug
> - you can adjust the ftrace buffer size at runtime. can we do that for > printk? I don't remember.
It may can't. The log buf can only be changed by bootargs: log_buf_len
Peter
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