linux-kernel - Re: [QUESTION] Is there a better way to get ftrace dump on guest?

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Message-ID: <CAM9d7ciGJiv7JZPq7B-qGz2vtQ9s7SnbTXgwEHwTO-jLPio0XQ@mail.gmail.com>
Date:	Tue, 28 Jun 2016 15:33:18 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	kvm@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan@...nel.org>
Subject: Re: [QUESTION] Is there a better way to get ftrace dump on guest?

Send again to correct addresses, sorry!

On Tue, Jun 28, 2016 at 3:25 PM, Namhyung Kim <namhyung@...nel.org> wrote:
> 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..