int __init round_jiffies_init(void)
{
printk("the round_jiffies test begin\n");
unsigned long j=jiffies; //记录当前节拍
unsigned long __result1=__round_jiffies(j,0); //参数j当前节拍，0是cpu编号
unsigned long __result2=__round_jiffies(j,1);//参数j当前节拍，1是cpu编号
unsigned long result1=round_jiffies(j);//参数j当前节拍
unsigned long result2=round_jiffies(j);//参数j当前节拍
printk("the jiffies is :%ld\n",j);//显示当前节拍
//显示函数调用结果
printk("the __result1 of __round_jiffies(j,0) is :%ld\n",__result1);
printk("the __result2 of __round_jiffies(j,1) is :%ld\n",__result2);
printk("the result1 of round_jiffies(j) is :%ld\n",result1);
printk("the result2 of round_jiffies(j) is :%ld\n",result2);
printk("<0>out round_jiffies_init");
return 0;
}
/**
* __round_jiffies_relative - function to round jiffies to a full second
* @j: the time in (relative) jiffies that should be rounded
* @cpu: the processor number on which the timeout will happen
*
* __round_jiffies_relative() rounds a time delta 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 exact rounding is skewed for each processor to avoid all
* processors firing at the exact same time, which could lead
* to lock contention or spurious cache line bouncing.
*
* The return value is the rounded version of the @j parameter.
*/
unsigned long __round_jiffies_relative(unsigned long j, int cpu)
{
/*
* In theory the following code can skip a jiffy in case jiffies
* increments right between the addition and the later subtraction.
* However since the entire point of this function is to use approximate
* timeouts, it's entirely ok to not handle that.
*/
return __round_jiffies(j + jiffies, cpu) - jiffies;
}
/**
* round_jiffies - function to round jiffies to a full second
* @j: the time in (absolute) jiffies that should be rounded
*
* 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.
*/
unsigned long round_jiffies(unsigned long j)
{
return __round_jiffies(j, raw_smp_processor_id());
}
