What is a jiffy in linux? - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Unix - 噫吁兮，危乎高哉

What is a jiffy in linux?

What is a jiffy in linux?# Unix - 噫吁兮，危乎高哉

F*e2002-09-26 07:09

1 楼

Say if I want to find the actual time of 100 jiffies on my linux,
how do I do it?
Thanks a lot!

c*e2002-09-26 07:09

2 楼

As I read it, jiffies are the number of elapsed ticks starting from
the system start. It's increment by 1 for every timer interrupt.
So that depends on how linux programs the programmable timer.
Normally, it's 10ms per tick.

【在 F**e 的大作中提到】

: Say if I want to find the actual time of 100 jiffies on my linux,
: how do I do it?
: Thanks a lot!

m*e2002-09-26 07:09

3 楼

In user space it's ALWAYS 100 jiffies per second (at least on x86).
In kernel space it depends. Recent kernels have changed it internally.

【在 c********e 的大作中提到】

: As I read it, jiffies are the number of elapsed ticks starting from
: the system start. It's increment by 1 for every timer interrupt.
: So that depends on how linux programs the programmable timer.
: Normally, it's 10ms per tick.

F*e2002-09-26 07:09

4 楼

Thank you, microbe and clarkmouse!
Actually my problem was: I was getting process info from
/proc//stat
One of the properties I am interested in is the usertime(utime) there. The man
says utime is "The number of jiffies that this process has been scheduled in
user mode".
So that means the number I get there divided by 100 will give me the number of
seconds? Right? Just want to make sure. Thanks.

【在 m*****e 的大作中提到】

:
: In user space it's ALWAYS 100 jiffies per second (at least on x86).
: In kernel space it depends. Recent kernels have changed it internally.