[lowrisc-dev] Support for Fedora / compressed extension

Dr Jonathan Kimmitt jrrk2 at cam.ac.uk
Mon Apr 2 13:02:25 BST 2018


If Fedora can run in spike with memory limited to 128M, then there is no 
reason why an upgraded Rocket with the C

extension cannot run it on an Nexys4DDR. But we cannot give a timescale 
to fix this because there are other unidentified

issues to be fixed as well. And it is a little difficult to rebase 
because major refactoring has gone on since then.

The biggest of these has been the introduction of TileLink-2, and it is 
not really practical to backport any of those features to the TileLink-1 
design that we have.

So our next release date and contents is uncertain, but as much IP and 
functionality as we can will be reused.

On 02/04/18 12:27, Manuel A. Fernandez Montecelo wrote:
> 2018-04-02 09:23 Dr Jonathan Kimmitt:
>> Dear Richard,
>>
>> My mistake, lowRISC-v0.5 runs a lightweight source based distribution 
>> based on RISCV-poky, using our modified 1.9.1 kernel and device 
>> drivers which have not been upstreamed. It would be perfectly 
>> possible to compile Fedora without compression but this would just 
>> move the bottleneck to a different place which is that the emulator 
>> is over a hundred times slower than a modern PC, and limited to 128M 
>> of RAM. Even running yum takes more than this at times. Swapping is 
>> also slow because it relies on individual writes to SD-card with 4 
>> bits @ 5MHz, which itself has internal latency. In addition network 
>> access is throttled to about 2 megabytes per second due to TCP stack 
>> and bus width considerations.
>>
>> With the best will in the world most mainstream distributions have 
>> more or less abandoned the embedded market by preferring heavyweight 
>> python based system tools which trade off memory for performance 
>> (feel free to dispute this sweeping generalisation, I know apt can 
>> run on the iPhone).  I am aware of course that Python has many 
>> benefits in robustness and foolproofing.
>
> apt is C++, though, and the main source of "memory usage" at runtime
> comes from the thousands of packages available in a full-fledged
> GNU/Linux distribution.
>
> Not sure in an FPGA, but it runs fine even in spike, AFAICR.
>
>
> Aside from this... dispute :) I suppose that Richard's question is more
> like: will you support the C extension at some point, so lowRISC will be
> able to run Fedora/Debian/etc. in the near future?
>
> One doesn't always need to run apt/dnf/yum etc. to be able to use
> thousands of packages precompiled.  One can just copy the file and
> install with dpkg or rpm for example, which are much less demanding.
>
>
> Cheers.




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