Re: [microblaze-uclinux] application's execution time

[Faiza Ait-Kaci <faiza.ak@xxxxxxxxxx>]

Hi,

Well actually, it is worse than that, the program hadn't stopped execution (even two hours after) I thought it took only one hour because I got a result on the screen but it was only an intermediate one.
I added another application which takes 0.02s to execute on my host (a matrix multiplication of 100*100 matrices). after two hours, the program was still running on target! I stopped the execution and tried a matrix multiplication of 10*4 matrices. the execution time on the target was of 0.01s.
Can this mean that only small programs can be run on target? Is that because of no MMU?

Thanks for answering.

Regards,

Faiza
----- Mail Original -----
De: "John Williams" <john.williams@xxxxxxxxxxxxx>
À: microblaze-uclinux@xxxxxxxxxxxxxx
Envoyé: Mardi 25 Août 2009 11h06:27 GMT +01:00 Amsterdam / Berlin / Berne / Rome / Stockholm / Vienne
Objet: Re: [microblaze-uclinux] application's execution time

Hi Faiza,

On Tue, Aug 25, 2009 at 6:36 PM, Faiza Ait-Kaci<faiza.ak@xxxxxxxxxx> wrote:

> I added a C++ application to the petalinux-dist and integrated it to the root file system image. executing it on the hardware platform, it took one hour to complete the execution!
> the program performs hundreds of iterations but on a pc it takes no more than a minute for execution. is that normal to have so a huge difference? what can slow down as much as that the execution?

What's the clock frequency of your PC, vs the system clock frequency
of the microblaze?

At a guess, maybe 3GHz vs 66Mhz?  There's a factor of 45 right there.
So, 1 minute -> 45 minutes.

Then, your PC has larger caches, so relatively fewer cache misses
(leading to sloooow DDR memory accesses), ...

The PC also has a much deeper pipeline, and multiple instruction issue
etc, so gets relatively more work done per clock cycle, and so it
goes.

So, even without knowing anything about what your app actually does,
it's not hard to see a factor of 60-100 there.

To get back to PC-like performance, you will need to think carefully
about the architecture of your system as a whole - data movement and
computation, across both application, kernel and hardware domains.

Regards,

John
-- 
John Williams, PhD, B.Eng, B.IT
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com  p: +61-7-30090663  f: +61-7-30090663
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