Hi,
--- James Yu <cyu021@xxxxxxxxx> escreveu:
> Dear all,
>
> I am doing the following in a kernel thread :
>
> ===== code segment=====
> prink("before mdelay:%d, ", jiffies);
> mdelay(300); // delay 300ms
> printk("after mdelay:%d\n", jiffies);
> ===== code segment=====
>
> However, jiffies before and after doing mdelay are the same!!!
> Can someone please explain why jiffies doesn't change ?
Probably between these 2 printks, no tick happened, so the jiffies
value was not incremented. Jiffies is incremented when a tick happens.
Perhaps you can check how is defined the HZ (depends on the arch) in
your kernel and figure out the frequency of tick rate.
I had this same problem when I tried to measure some stuffs in the
schedule. Jiffies did not change in some situations. So I used
sched_clock() that provide the time in nanoseconds.
BR,
Mauricio Lin.
> Cheers,
> --
> James
> cyu021@xxxxxxxxx
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
>
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