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Re: jiffie



On Sun, Dec 05, 2004 at 03:43:05PM +0100, Paul Akkermans wrote:
> Can anybody tell me what a jiffie is? I've been seeing this term all through the kernel code.

I found this on the net:

> Under Linux the jiffies variable is the number of clock ticks since the
> machine boot. It's rate is defined by (surprise, surprise...) the HZ define
> from the kernel param.h
> 
> For a normal (as in - not patched) Linux kernel of versions 2.4.x the value
> of HZ is 100 for the x86 platform and a 1000 for the PowerPC platform. Since
> version 2.6 the x86 port also has a value of 1000 for HZ by default. Patches
> exist to make these variable during compile time.
> 
> One issue that is very important to consider is "jiffie warp". The jiffie is
> a 32 bit value, which means it will wrap around somewhere after a year for
> kernel 2.4/x86 and much sooner for 2.6 kernels or on the powerpc.

http://www.mail-archive.com/asterisk-dev@lists.digium.com/msg06930.html


Sam



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