>>>>> "Chris" == Chris Friesen <[email protected]> writes:
Chris> 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.
Chris> Most cpus have some way of getting at a counter or decrementer
Chris> of various frequencies. Usually it requires low-level hardware
Chris> knowledge and often it needs assembly code.
As a device driver is inside the linux kernel (unless you're writein a
user-mode device driver :-)) you can use the getcycles() macro that's
defined for most architectures. It provides a snapshot of the
cycle-counter.
Caveats:
1. If you're running with power management, the cycle
counter ticks at a variable rate.
2. If you're on a multiprocessor, the cycle counters of
different processors need not be synchronised.
--
Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au
The technical we do immediately, the political takes *forever*
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