OS4E

[mrgs]

@fmotta: Thank You for Your note. I will check OS-9, as another OS(s) to pick up nice ideas. But as I have written: I do not like to port an OS, I would like to build one from 'scratch'. --- My pleasure to see You here and additionally: You are talking about an OS not a 'bare-code' solution. ---

@ysapir: Thank You for Your answers. Well, "To set to count clock cycles for TIMER" is just the first step for a nice RTC. Additionally we need more: - freq_of_CPU >> freq_of_TIMER; - nice (efficient/quick/well designed) IT handler routine, - OS needs to remain minimum time at IT masked state ... OK. Forget it. Thank You again. Regards, Gabor.

[mrgs]

[Oneill]

Hi, Looks good. I would vote for the first one.
It is simple and elegant.
I hope that will be the reaction for the OS4E design and implementation.
Regards,
Oneill

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Dear Oneill, Thank You for Your positive feedback. 'Cool' logo is just a very beginning of OS4E. I have just almost finalized all 'functions' so, I am very close to share my SW repository access. Here You can follow the developing process. Nothing working yet, 'just' a skeleton now. Regards, Gabor

[notzed]

[mrgs]

@notzed: First of all, thank You for Your comment/suggestion. Well, 10 years ago I have designed/implemented a little cooperative multitasking RT system for a uC. It was a 'precise miracle' and a very nice 'trip' for me. Without any HW support: 2xUART, I2C, RTC, E2PROM log, RS485 bus protocol on 4K, ... How can I say?! I have to check: what can I achieve with a preemptive OS.

Well, as I see the Epiphany CPU/Parallella Platform at this moment, the key question is not the context switch, rather than memory management, as You marked the 'current' weakest points as: no MMU. Well, maybe I am wrong, but at now I 'believe' that I can build up a 'nice' memory management system without a CPU based MMU. How?!

Well, start to the easiest point. As, You mentioned: - I will protect the page(s) dynamically with the RO flags which provide by the CPU, and there will be a flat memory map. Not so interest. But IMHO: possible to build up a multitasking system without MMU.

MMU: So, what is the root of the problem: We have to 'generate' each addresses on runtime. Where are the 'compiled addresses'? At the 'file system', then the 'DDR RAM'. How can we deliver the code and the data into the Epiphany? Via FPGA and CPU DMA. So, 'theoretically' we can use the FPGA like an external MMU. Oh... what a 'crazy' idea?!

A few days ago I just start to wondering: What if: Put an illegal, but definite instruction code before all memory address instruction, to support the memory management. (NON exist MMU case). Then generate the new address with the exception handler?! What do You think? ...

I am going to check CELL BE-s solution. Thank You. Regards, Gabor --- let me have Your feedbacks(!) thank You(!) ---

[notzed]

[mrgs]

[fredd]

[mrgs]

@fredd : My pleasure to read Your comment. Well, step by step:

(#1) “dynamical addressing” : Tell the true, I was very close to put THIS key question for SW guys whois going to port Erlang, Python, ..., another interpreter / virtual machine OR 'just' libraries. How these clever guys will deliver enough 'RAM' for their SWs. So, thanks for You, at now I am sure we have the same 'challenge'.

(#2) “OS v.s. dynamic language” : At the beginning I have had a 'doubt': an OS or virtual machines for a nice language. BUT(!) day by day I realized: (a) at finally 'a language' wants a same environment like just an OS can deliver (memory/scheduling/IO...) (b) which language?! (c) I really want to try out myself to write an OS. ('sorry' about this).

(#3) “FPGA” : You, as a sw person win(!) an another language: VHDL. Welcome on the board 'de' Parallella.

(#4) “chunk” : I can accept that, You are thinking about chunk/slice. Well, I have not finalized low/high memory management system of OS4E. I agree (a main point), compiler should support 'us' its own way, but I do not want so much as You written at Your sample.

(#5) “core-private, read-only, core-to-core, message-passing...” : In my point of view these also the area of the OS not an 'in-compiled function' in an application. But I think, Your idea will work well too.

(#6) “DMA” : Should work 'without' CPU. This is why we call it DMA. - There was an another issue/topic, as I understand it, it talks about the 'remote SDRAM' access. 'Solution' is the DMA(!) -

(#7) “extended memory management” : It will bring not 'just' the 'transparency', but a very good opportunity for a flexible, 'all language' supported system. - It is necessary but not sufficient condition for a 'real' OS on Epiphany. - I think, we should share our results 'soon'.

Regards, Gabor