问题描述
如何在Linux中手动将抖动转换为毫秒，反之亦然?我知道内核2.6具有此功能，但是我正在研究2.4(家庭作业)，尽管我查看了代码，但它使用了许多宏常量，我不知道它们是否在2.4中定义.
How do I manually convert jiffies to milliseconds and vice versa in Linux? I know kernel 2.6 has a function for this, but I'm working on 2.4 (homework) and though I looked at the code it uses lots of macro constants which I have no idea if they're defined in 2.4.
推荐答案
如先前的回答所述，jiffies递增的速率是固定的.
As a previous answer said, the rate at which jiffies increments is fixed.
为接受jiffies的函数指定时间的标准方法是使用常量HZ.
The standard way of specifying time for a function that accepts jiffies is using the constant HZ.
这是赫兹(Hertz)的缩写，或每秒的刻度数.在计时器刻度设置为1ms的系统上，HZ = 1000.某些发行版或体系结构可能使用另一个数字(以前是100).
That's the abbreviation for Hertz, or the number of ticks per second. On a system with a timer tick set to 1ms, HZ=1000. Some distributions or architectures may use another number (100 used to be common).
为函数指定jiffies计数的标准方法是使用HZ，如下所示:
The standard way of specifying a jiffies count for a function is using HZ, like this:
schedule_timeout(HZ / 10); /* Timeout after 1/10 second */
在大多数简单情况下，这都可以正常工作.
In most simple cases, this works fine.
2*HZ /* 2 seconds in jiffies */
HZ /* 1 second in jiffies */
foo * HZ /* foo seconds in jiffies */
HZ/10 /* 100 milliseconds in jiffies */
HZ/100 /* 10 milliseconds in jiffies */
bar*HZ/1000 /* bar milliseconds in jiffies */
后两个问题有点问题，例如，在具有10 ms计时器滴答的系统上，HZ/100为1，精度开始受到影响.您可能会在0.0001到1.999之间的任何时间间隔内获得延迟(本质上是0-2毫秒).如果您尝试在10ms的滴答系统上使用HZ/200，则整数除法会给您0个jiffies！
Those last two have a bit of a problem, however, as on a system with a 10 ms timer tick, HZ/100 is 1, and the precision starts to suffer. You may get a delay anywhere between 0.0001 and 1.999 timer ticks (0-2 ms, essentially). If you tried to use HZ/200 on a 10ms tick system, the integer division gives you 0 jiffies!
因此，经验法则是，请小心使用HZ来获取微小值(接近1吉菲).
So the rule of thumb is, be very careful using HZ for tiny values (those approaching 1 jiffie).
要进行另一种转换，您可以使用:
To convert the other way, you would use:
jiffies / HZ /* jiffies to seconds */
jiffies * 1000 / HZ /* jiffies to milliseconds */
您不应期望比毫秒精度更好的东西.
You shouldn't expect anything better than millisecond precision.
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