Hi Daniel,

On 01/29/2014 08:08 AM, Daniel Waddington wrote:

Can someone give me a guestimate (or better) on the minimum RAM and ROM footprints for ARM (lets say PBXA9) for genode-hw and genode+foc, to run a minimal printf program?

I just did a small experiment (see the attached patch). To determine how much RAM is needed to run the test-printf on hw_pbxa9, I successively shrunk the physical RAM visible to base-hw. Of the two RAM regions of the PBX-A9 platform, I kept only RAM0, starting at 0x70000000. This is the address where the boot image is loaded to.

Apparently, setting RAM0_SIZE to 0x240000 (ca. 2.3 MiB) is enough to run core + init + test-printf on PBX-A9 via base-hw.

I think that a further reduction is possible but it will take a bit more work. Also, compiling the system with -Os would eventually help to get the value smaller.

Also, I wonder if there are other open source microkernels aimed at tiny memory footprints - can you suggest any?

Sorry, I'm afraid that I cannot recommend a suitable kernel from the tip of my head. However, once I stumbled over the following project at GitHub, which looks pretty interesting (I have not tried it through):

https://github.com/f9micro/f9-kernel

Cheers Norman

Hi Christian and Norman Thanks for the quick responses. So do you think it's fair to say that realistically 4MB is a probably the smallest you could do anything useful with. I know useful is hard to define.

Daniel On Jan 29, 2014 5:02 AM, "Christian Helmuth" < christian.helmuth@...1...> wrote:

Hello,

On Wed, Jan 29, 2014 at 12:35:55PM +0100, Norman Feske wrote:

...

Apparently, setting RAM0_SIZE to 0x240000 (ca. 2.3 MiB) is enough to run core + init + test-printf on PBX-A9 via base-hw.

I did a quick check for foc_pbxa9 with the attached patch. The smallest working amount of RAM was 0x135000 (ca. 1.2 MiB), but this is without the RAM used by the Fiasco kernel in the scenario. From the Fiasco kernel debugger I got "Used 2445KB out of 16384KB of Kmem" with the command 'km'.

Additionally, we have to add the amount of RAM used by ROM modules (currently loaded to RAM by the bootloader), which sums up to ca. 2.3 MiB on foc_pbxa9.

Regards

Christian Helmuth Genode Labs

http://www.genode-labs.com/ · http://genode.org/ https://twitter.com/GenodeLabs · /ˈdʒiː.nəʊd/

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