[Vm-dev] [Pharo-dev] shallowCopy problem on 64 bit Pharo ?

tim Rowledge tim at rowledge.org
Sun Feb 5 19:25:46 UTC 2017

> On 05-02-2017, at 5:08 AM, Clément Bera <bera.clement at gmail.com> wrote:
> I remember there was a discussion about that somewhere but I can't find it. I cc vm-dev they may have a clue.
> When copying a pointer object in 64 bits instead of 32 bits, you need to copy twice many data, so it is going to be slower in any case. 

Err, not really. Probably. Assuming you have a 64 bit cpu etc, of course. And dependent on details of the memory architecture outside the cpu too - after all many systems do not need the memory chip organisation to match the cpu word size, having multiple lanes, burst read cache loading, even heterogenous regions (I suspect mostly in embedded systems for that, but y’never know).

Yes, you’re moving twice as much stuff but it will still be a single read & write per word. After that you’re at the mercy of cache lines, write buffers, chip specs and not to mention the Hamsters.

tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
We can rescue a hostage or bankrupt a system. Now, what would you like us to do?

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