hrtimer: Make offset update smarter

hrtimer: Make offset update smarter

On every tick/hrtimer interrupt we update the offset variables of the
clock bases. That's silly because these offsets change very seldom.

Add a sequence counter to the time keeping code which keeps track of
the offset updates (clock_was_set()). Have a sequence cache in the
hrtimer cpu bases to evaluate whether the offsets must be updated or
not. This allows us later to avoid pointless cacheline pollution.

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Preeti U Murthy <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Viresh Kumar <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: John Stultz <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: John Stultz <[email protected]>