On Mon, 28 Mar 2005, Chris Friesen wrote:
> Date: Mon, 28 Mar 2005 23:07:14 -0600
> From: Chris Friesen <[EMAIL PROTECTED]>
> To: krishna <[EMAIL PROTECTED]>
> Cc: Linux Kernel <linux-kernel@vger.kernel.org>
> 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
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