From 2924ecd441f3c12da59b297daade265f49d0831b Mon Sep 17 00:00:00 2001 From: Joel Fernandes Date: Mon, 28 Nov 2016 14:35:24 -0800 Subject: 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 Signed-off-by: John Stultz Reviewed-by: Thomas Gleixner Acked-by: Steven Rostedt Cc: Prarit Bhargava Cc: Richard Cochran Link: http://lkml.kernel.org/r/1480372524-15181-8-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner --- Documentation/trace/ftrace.txt | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'Documentation/trace') diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index 185c39fea2a0..5596e2d71d6d 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 -- cgit v1.2.3