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SubjectRe: How to measure time accurately.
>>>>> "Chris" == Chris Friesen <> 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

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 peterc AT
The technical we do immediately, the political takes *forever*
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