SuSE 11.3 - man page for round_jiffies (suse section 9)

ROUND_JIFFIES(9)			  Driver Basics 			 ROUND_JIFFIES(9)

NAME
       round_jiffies - function to round jiffies to a full second

SYNOPSIS
       unsigned long round_jiffies(unsigned long j);

ARGUMENTS
       j
	   the time in (absolute) jiffies that should be rounded

DESCRIPTION
       round_jiffies rounds an absolute time in the future (in jiffies) up or down to
       (approximately) full seconds. This is useful for timers for which the exact time they fire
       does not matter too much, as long as they fire approximately every X seconds.

       By rounding these timers to whole seconds, all such timers will fire at the same time,
       rather than at various times spread out. The goal of this is to have the CPU wake up less,
       which saves power.

       The return value is the rounded version of the j parameter.

COPYRIGHT
Kernel Hackers Manual 2.6.		    July 2010				 ROUND_JIFFIES(9)