[Cuis] Cuis on Stack VM on Raspberry Pi

[Juan Vuletich]

On 7/21/2013 6:08 PM, Casey Ransberger wrote:
> 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.
>

Cool. Nice to know. Thanks!

Cheers,
Juan Vuletich