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    Subject[tip:timers/core] trace: Update documentation for mono, mono_raw and boot clock
    Commit-ID:  2924ecd441f3c12da59b297daade265f49d0831b
    Gitweb: http://git.kernel.org/tip/2924ecd441f3c12da59b297daade265f49d0831b
    Author: Joel Fernandes <joelaf@google.com>
    AuthorDate: Mon, 28 Nov 2016 14:35:24 -0800
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Tue, 29 Nov 2016 18:03:00 +0100

    trace: Update documentation for mono, mono_raw and boot clock

    Documentation was missing for mono and mono_raw, add them and also for
    the boot clock introduced in this series.

    Signed-off-by: Joel Fernandes <joelaf@google.com>
    Signed-off-by: John Stultz <john.stultz@linaro.org>
    Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
    Acked-by: Steven Rostedt <rostedt@goodmis.org>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Cc: Richard Cochran <richardcochran@gmail.com>
    Link: http://lkml.kernel.org/r/1480372524-15181-8-git-send-email-john.stultz@linaro.org
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

    ---
    Documentation/trace/ftrace.txt | 20 ++++++++++++++++++++
    1 file changed, 20 insertions(+)

    diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
    index 185c39f..5596e2d 100644
    --- a/Documentation/trace/ftrace.txt
    +++ b/Documentation/trace/ftrace.txt
    @@ -362,6 +362,26 @@ of ftrace. Here is a list of some of the key files:
    to correlate events across hypervisor/guest if
    tb_offset is known.

    + mono: This uses the fast monotonic clock (CLOCK_MONOTONIC)
    + which is monotonic and is subject to NTP rate adjustments.
    +
    + mono_raw:
    + This is the raw monotonic clock (CLOCK_MONOTONIC_RAW)
    + which is montonic but is not subject to any rate adjustments
    + and ticks at the same rate as the hardware clocksource.
    +
    + boot: This is the boot clock (CLOCK_BOOTTIME) and is based on the
    + fast monotonic clock, but also accounts for time spent in
    + suspend. Since the clock access is designed for use in
    + tracing in the suspend path, some side effects are possible
    + if clock is accessed after the suspend time is accounted before
    + the fast mono clock is updated. In this case, the clock update
    + appears to happen slightly sooner than it normally would have.
    + Also on 32-bit systems, it's possible that the 64-bit boot offset
    + sees a partial update. These effects are rare and post
    + processing should be able to handle them. See comments in the
    + ktime_get_boot_fast_ns() function for more information.
    +
    To set a clock, simply echo the clock name into this file.

    echo global > trace_clock
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