From mboxrd@z Thu Jan  1 00:00:00 1970
From: Namhyung Kim <namhyung@kernel.org>
Subject: [QUESTION] Is there a better way to get ftrace dump on guest?
Date: Tue, 28 Jun 2016 15:25:14 +0900
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Cc: lkml@vger.kernel.org, Minchan Kim <minchan@kernel.org>
To: kvm@vger.kernel.org, Steven Rostedt <rostedt@goodmig.org>
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Hello,

I'm running some guest machines for kernel development.  For debugging
purpose, I use lots of trace_printk() since it's faster than normal
printk().  When kernel crash happens the trace buffer is printed on
console (I set ftrace_dump_on_oops) but it takes too much time.  I
don't want to reduce the size of ring buffer as I want to collect the
debug info as much as possible.  And I also want to see trace from all
cpu so 'ftrace_dump_on_oop = 2' is not an option.

I know the kexec/kdump (and the crash tool) can dump and analyze the
trace buffer later.  But it's cumbersome to do it everytime and more
importantly, I don't want to spend the memory for the crashkernel.

So what is the best way to handle this?  I'd like to know how others
setup the debugging environment..

Thanks,
Namhyung