[Vm-dev] oops to zero
hmm at heeg.de
Fri Oct 5 12:43:21 UTC 2007
Bert Freudenberg schrieb:
> On Oct 5, 2007, at 5:05 , Keith Hodges wrote:
>> Indeed you make a good point, if we can pick a good number that
>> runtimes can use without traversing the image then great. What number
>> should it be?
> I don't think any OS (except for DOS maybe) would guarantee you a
> specific start address.
It does not need to guarantee a start address but just pick the same one
most of the time (for example, as long as the VM binary stays the same).
I think Squeak already does this. See below for another option.
>> Since OLPC applications have a virtual linux box to themselves can we
>> just pick a number that suits us/them?
> I wouldn't think so ... but it is an interesting idea. I will ask the
> OLPC guys.
It's not difficult for a VM to use mmap() on /dev/null (or was it
/dev/zero?) to allocate memory for the image to any given address under
linux (as long as the CPU/OS version supports memory at that address).
If a VM did this, it could have a fixed image start address even across
VM versions. Even cooler would be to mmap() the image file directly with
copy-on-write behavior for almost instantaneous startup.
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