Commit 3fdb14fd authored by Thomas Gleixner's avatar Thomas Gleixner Committed by John Stultz
Browse files

timekeeping: Cache optimize struct timekeeper 



struct timekeeper is quite badly sorted for the hot readout path. Most
time access functions need to load two cache lines.

Rearrange it so ktime_get() and getnstimeofday() are happy with a
single cache line.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent c905fae4

include/linux/timekeeper_internal.h

+46 −38
Original line number Diff line number Diff line
@@ -10,7 +10,22 @@ 
#include <linux/jiffies.h>

#include <linux/time.h>



/* Structure holding internal timekeeping values. */

/*

 * Structure holding internal timekeeping values.

 *

 * Note: wall_to_monotonic is what we need to add to xtime (or xtime

 * corrected for sub jiffie times) to get to monotonic time.

 * Monotonic is pegged at zero at system boot time, so

 * wall_to_monotonic will be negative, however, we will ALWAYS keep

 * the tv_nsec part positive so we can use the usual normalization.

 *

 * wall_to_monotonic is moved after resume from suspend for the

 * monotonic time not to jump. We need to add total_sleep_time to

 * wall_to_monotonic to get the real boot based time offset.

 *

 * - wall_to_monotonic is no longer the boot time, getboottime must be

 * used instead.

 */

struct timekeeper {

	/* Current clocksource used for timekeeping. */

	struct clocksource	*clock;
@@ -18,6 +33,29 @@ struct timekeeper { 
	u32			mult;

	/* The shift value of the current clocksource. */

	u32			shift;

	/* Clock shifted nano seconds */

	u64			xtime_nsec;



	/* Current CLOCK_REALTIME time in seconds */

	u64			xtime_sec;

	/* CLOCK_REALTIME to CLOCK_MONOTONIC offset */

	struct timespec64	wall_to_monotonic;



	/* Offset clock monotonic -> clock realtime */

	ktime_t			offs_real;

	/* Offset clock monotonic -> clock boottime */

	ktime_t			offs_boot;

	/* Offset clock monotonic -> clock tai */

	ktime_t			offs_tai;



	/* time spent in suspend */

	struct timespec64	total_sleep_time;

	/* The current UTC to TAI offset in seconds */

	s32			tai_offset;



	/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */

	struct timespec64	raw_time;



	/* Number of clock cycles in one NTP interval. */

	cycle_t			cycle_interval;

	/* Last cycle value (also stored in clock->cycle_last) */
@@ -29,46 +67,16 @@ struct timekeeper { 
	/* Raw nano seconds accumulated per NTP interval. */

	u32			raw_interval;



	/* Current CLOCK_REALTIME time in seconds */

	u64			xtime_sec;

	/* Clock shifted nano seconds */

	u64			xtime_nsec;



	/* Difference between accumulated time and NTP time in ntp

	 * shifted nano seconds. */

	/*

	 * Difference between accumulated time and NTP time in ntp

	 * shifted nano seconds.

	 */

	s64			ntp_error;

	/* Shift conversion between clock shifted nano seconds and

	 * ntp shifted nano seconds. */

	u32			ntp_error_shift;



	/*

	 * wall_to_monotonic is what we need to add to xtime (or xtime corrected

	 * for sub jiffie times) to get to monotonic time.  Monotonic is pegged

	 * at zero at system boot time, so wall_to_monotonic will be negative,

	 * however, we will ALWAYS keep the tv_nsec part positive so we can use

	 * the usual normalization.

	 *

	 * wall_to_monotonic is moved after resume from suspend for the

	 * monotonic time not to jump. We need to add total_sleep_time to

	 * wall_to_monotonic to get the real boot based time offset.

	 *

	 * - wall_to_monotonic is no longer the boot time, getboottime must be

	 * used instead.

	 * Shift conversion between clock shifted nano seconds and

	 * ntp shifted nano seconds.

	 */

	struct timespec64	wall_to_monotonic;

	/* Offset clock monotonic -> clock realtime */

	ktime_t			offs_real;

	/* time spent in suspend */

	struct timespec64	total_sleep_time;

	/* Offset clock monotonic -> clock boottime */

	ktime_t			offs_boot;

	/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */

	struct timespec64	raw_time;

	/* The current UTC to TAI offset in seconds */

	s32			tai_offset;

	/* Offset clock monotonic -> clock tai */

	ktime_t			offs_tai;



	u32			ntp_error_shift;

};



#ifdef CONFIG_GENERIC_TIME_VSYSCALL

kernel/time/timekeeping.c

+97 −88

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