[Cuis] Cuis on Stack VM on Raspberry Pi

[Casey Ransberger]

Hi Hannes,

Tim's changes are mostly focused around making Scratch perform well on the Pi (read: ARM6, narrow memory bus, small memory, hardware float weirdness, SD storage, 700mhz proc, etc)  but the upshot is, he's ripped a lot of cruft out of BitBlt (if you think about it, speeding this up yields a lot of performance gains, as it's called every time a Morphic frame is rendered, not to mention any time a block of memory is copied.)

In addition to general cleanup and performance tuning to BitBlt, he's also added some native code to optimize things a bit more wrt the particular peculiarities of BitBlt on ARM (which of course will only be present in an ARM VM.)

Of course all I did was offer to build the VM on my Pi and throw in on testing. I might have the exact details wrong in the above, but that's the gist of what's going on. 

This VM really does seem a lot more responsive than the interpreter did on the Pi, in spite of that I was expecting "modest" gains from the stack orientation and the generation scavenging GC. I think it maybe has to do with the fact that the memory bus is narrow, and the Stack VM doesn't usually allocate temps on the heap. Dunno. 


On Jul 21, 2013, at 9:27 AM, "H. Hirzel" <hannes.hirzel at gmail.com> wrote:

> On 7/21/13, Ken Dickey <Ken.Dickey at whidbey.com> wrote:
>> On Sun, 21 Jul 2013 00:55:34 -0700
>> Casey Ransberger <casey.obrien.r at gmail.com> wrote:
>> 
>>> I've got the latest Cuis running on a custom Stack VM courtesy of Tim
>>> Rowledge.
> 
> Great!
> 
> Where did you compile the VM? On the R-Pi?
> 
> Could you please list  a few features of what is custom?
> 
> --Hannes
> 
> This could come in handy for perf testing. If anyone has any
>>> bits
>>> they'd like me to squeeze through the eye of the needle with this thing,
>>> let me know, and if I've got the time I will.
>> 
>> Good news indeed!
>> 
>> What does the rest of the software ecology look like?  [Which Linux?  FFI up
>> with device access?]
>> 
>> Cheers,
>> -KenD
>> --
>> Ken [dot] Dickey [at] whidbey [dot] com
>> 
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