clocksource: Restructure clocksource struct members

Group the hot path members of struct clocksource together so we have a
better cache line footprint. Make it cacheline aligned.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Link: http://lkml.kernel.org/r/%3C20110518210136.003081882%40linutronix.de%3E

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0fb0b7e..c918fbd 100644 (file)
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -159,42 +159,38 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
  */
 struct clocksource {
        /*
-        * First part of structure is read mostly
+        * Hotpath data, fits in a single cache line when the
+        * clocksource itself is cacheline aligned.
         */
-       const char *name;
-       struct list_head list;
-       int rating;
        cycle_t (*read)(struct clocksource *cs);
-       int (*enable)(struct clocksource *cs);
-       void (*disable)(struct clocksource *cs);
+       cycle_t cycle_last;
        cycle_t mask;
        u32 mult;
        u32 shift;
        u64 max_idle_ns;
-       unsigned long flags;
-       cycle_t (*vread)(void);
-       void (*suspend)(struct clocksource *cs);
-       void (*resume)(struct clocksource *cs);
+
 #ifdef CONFIG_IA64
        void *fsys_mmio;        /* used by fsyscall asm code */
 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      ((mmio) = (addr))
 #else
 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      do { } while (0)
 #endif
-
-       /*
-        * Second part is written at each timer interrupt
-        * Keep it in a different cache line to dirty no
-        * more than one cache line.
-        */
-       cycle_t cycle_last ____cacheline_aligned_in_smp;
+       const char *name;
+       struct list_head list;
+       int rating;
+       cycle_t (*vread)(void);
+       int (*enable)(struct clocksource *cs);
+       void (*disable)(struct clocksource *cs);
+       unsigned long flags;
+       void (*suspend)(struct clocksource *cs);
+       void (*resume)(struct clocksource *cs);
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
        /* Watchdog related data, used by the framework */
        struct list_head wd_list;
        cycle_t wd_last;
 #endif
-};
+} ____cacheline_aligned;
 
 /*
  * Clock source flags bits::