[haiku] Re: Fwd: x86_64 build failed with gcc4 based x86_64 linux distros

Le mercredi 27 juillet 2011 à 17:44 +0200, Stephan Assmus a écrit :
> Am 27.07.2011 15:46, schrieb Andrew Hudson:
> >> But really, the intended target for Haiku doesn't really need that much
> >> yet.
> >
> > OK, thanks for the info. Yes, I agree that 4 GB is good enough for basic
> > purposes. However, the definition of a successful product is when people
> > use it for unintended purposes :-) - Andrew
> 
> I don't quite agree with Françoi's wording: What currently is or is not 
> a feature of Haiku is much less the product of target audience 
> considerations, but much more the product of who (including "nobody") 
> had the time and motivation to implement what code.

Yeah right, but for now I'm more interested into the ARM and m68k ports
than x86_64 :P

> That being said, I believe the point of implementing PAE support (yes it 
> exists) was to be able to address more than 4 GB. Each individual 
> process in Haiku can only address 4GB, but the kernel should be able to 
> use more than 4GB for the mapping of virtual to physical memory. That is 

Yep, the PAE paging code uses 64bit types to hold the physical
addresses, which seems to be 40bit according to the bitmasks in paging.h

> of course only interesting when more than one process is running at a 
> time, and affects the necessity for swapping out pages. For example, 
> when one process indeed uses all of it's 4GB address space, the Haiku 
> kernel does not necessarily need to swap out virtual memory, when there 
> are more then 4GB available in physical RAM, since the address space of 
> another process could be mapped to another range of the physical memory. 
> Hope I have remembered these details correctly.

Yeah, one of the few useful cases for us that I see would be VirtualBox,
once the port is done :p

François.


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