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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 46 insertions, 38 deletions

diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 16de6d7c240a..2cb96235c249 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -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