vdso: Make vdso_time_data cacheline aligned

vdso_time_data is not cacheline aligned at the moment. When instantiating
an array, the start of the second array member is not cache line aligned.

This increases the number of the required cache lines which needs to be
read when handling e.g. CLOCK_MONOTONIC_RAW, because the data spawns an
extra cache line if the previous data does not end at a cache line
boundary.

Therefore make struct vdso_time_data cacheline aligned.

Signed-off-by: Anna-Maria Behnsen <[email protected]>
Signed-off-by: Nam Cao <[email protected]>
Signed-off-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: anna-marialx

include/vdso/datapage.h

@@ -11,6 +11,7 @@
 
 #include <vdso/align.h>
 #include <vdso/bits.h>
+#include <vdso/cache.h>
 #include <vdso/clocksource.h>
 #include <vdso/ktime.h>
 #include <vdso/limits.h>
@@ -126,7 +127,7 @@ struct vdso_time_data {
 	u32			__unused;
 
 	struct arch_vdso_time_data arch_data;
-};
+} ____cacheline_aligned;
 
 /**
  * struct vdso_rng_data - vdso RNG state information