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From: John Stultz <john.stultz@linaro.org>
Date: Tue, 1 Aug 2017 10:40:47 -0700
Message-ID: <CALAqxLX=T=7HJu5TV7rjFAE+4fmV0wNQeyiyW66Uj7UT_-TmXQ@mail.gmail.com>
Subject: Re: [PATCH v2] printk: Add boottime and real timestamps
To: Prarit Bhargava <prarit@redhat.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
        Mark Salyzyn <salyzyn@android.com>, Jonathan Corbet <corbet@lwn.net>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Christoffer Dall <cdall@linaro.org>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Joel Fernandes <joelaf@google.com>,
        Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Nicholas Piggin <npiggin@gmail.com>,
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        Olof Johansson <olof@lixom.net>, Josh Poimboeuf <jpoimboe@redhat.com>,
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On Tue, Aug 1, 2017 at 10:35 AM, Prarit Bhargava <prarit@redhat.com> wrote:
>
>
> On 08/01/2017 01:00 PM, John Stultz wrote:
>> Is there a reason your not also adding PRINTK_TIME_BOOT here (which to
>> me would be more generally useful then REAL or MONO)?
>
> REAL has been useful to me in debug cases where events on the system were timed
> to the wall clock (ex cron job running at 3AM).  I hadn't really thought much
> about using BOOT TBH because MONO seemed to work just fine.
>
> Mark Salyzyn, did you want BOOT or MONO?

I know Mark has specific formatting needs, so I'm not going to speak
for him, but BOOT is actually a nice improvement over MONO, since it
includes suspend time, and avoids inconsistencies due to userspace
tweaking the time, which REALTIME has.  So for debugging suspend
related issues and being able to understand how much time a system has
spent in suspend vs not it would be quite useful.

thanks
-john