[botan-devel] Set the cpu speed in the environment or command line for ./botan speed

Uri Blumenthal uri at mit.edu
Thu Mar 8 07:52:16 EST 2018

I'd like to see something like --cpu-clock-speed, instead of or in addition to the --cpu-clock-ratio.

Reason: for some CPUs one *cannot accurately* measure their clocks, so an approach that requires knowing *both* the measured and the claimed clocks is bound to fail. Which is why what @noloader is asking for makes perfect sense.

Sent from my test iPhone

> On Mar 8, 2018, at 05:42, Jack Lloyd <jack at randombit.net> wrote: 
>> On Wed, Mar 07, 2018 at 08:13:33PM -0500, Jeffrey Walton wrote:
>> Hi Everyone,
>> I'm looking for a way to set the cpu speed in the environment or from
>> the command line when running ./botan speed.
> This doesn't exist in 2.4 but in master (upcoming 2.5) you can use the
> option --cpu-clock-ratio which expresses a ratio between the measured
> CPU clocks and the actual CPU clocks. This was added for POWER8 which
> has a fixed 512 MHz timebase, regardless of what the processor is
> running at. So for example on a 3.0 GHz POWER8 you would use
> --cpu-clock-ratio=.17 (.17 ~ 512/3000) so that CPU clocks are reported
> correctly.
> Worth mentioning we don't have any code for getting the cycle counter
> on ARM or MIPS so for IoT this will not be useful anyway.
> Jack
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