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Commit 92af4dcb authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

tracing: Unify the "boot" and "mono" tracing clocks 



Unify the "boot" and "mono" tracing clocks and document the new behaviour.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Easton <kevin@guarana.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20180301165150.489635255@linutronix.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 127bfa5f

Documentation/trace/ftrace.txt

+3 −11
Original line number Diff line number Diff line
@@ -449,17 +449,9 @@ of ftrace. Here is a list of some of the key files: 
		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.

	  boot: Same as mono. Used to be a separate clock which accounted

	  	for the time spent in suspend while CLOCK_MONOTONIC did

		not.



	To set a clock, simply echo the clock name into this file.

include/linux/timekeeping.h

+0 −6
Original line number Diff line number Diff line
@@ -113,12 +113,6 @@ extern u64 ktime_get_mono_fast_ns(void); 
extern u64 ktime_get_raw_fast_ns(void);

extern u64 ktime_get_real_fast_ns(void);



/* Clock BOOTTIME compatibility wrappers */

static inline u64 ktime_get_boot_fast_ns(void)

{

	return ktime_get_mono_fast_ns();

}



/*

 * timespec64 interfaces utilizing the ktime based ones

 */

kernel/trace/trace.c

+1 −1
Original line number Diff line number Diff line
@@ -1164,7 +1164,7 @@ static struct { 
	{ trace_clock,			"perf",		1 },

	{ ktime_get_mono_fast_ns,	"mono",		1 },

	{ ktime_get_raw_fast_ns,	"mono_raw",	1 },

	{ ktime_get_boot_fast_ns,	"boot",		1 },

	{ ktime_get_mono_fast_ns,	"boot",		1 },

	ARCH_TRACE_CLOCKS

};