[lkml]   [2005]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: How to measure time accurately.
On Mon, 28 Mar 2005, Chris Friesen wrote:

> Date: Mon, 28 Mar 2005 23:07:14 -0600
> From: Chris Friesen <>
> To: krishna <>
> Cc: Linux Kernel <>
> Subject: Re: How to measure time accurately.
> krishna wrote:
> > Hi All,
> >
> > Can any one tell me how to measure time accurately for a block of C code in
> > device drivers.
> > For example, If I want to measure the time duration of firmware download.
> Most cpus have some way of getting at a counter or decrementer of various
> frequencies. Usually it requires low-level hardware knowledge and often it
> needs assembly code.
> On ppc you'd use the mftbu/mftbl instructions, as suggested by Lee on x86
> you'd use the rdtsc instruction.

In some cases you can simply count jiffies - depending on how accurate you
need to time things I'd say that often something like this is adequate :

unsigned long start, time_spent;

start = jiffies;
/* do stuff */
time_spent = jiffies - start;
printk("stuff took %d jiffies (%d seconds)\n", time_spent, time_spent/HZ);

Jesper Juhl

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-04-06 13:31    [W:0.036 / U:3.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site