Re: Resolved: Unexpected page fault from 0xdc003 ad address 0x??

[Bas Wijnen]

Marcus Brinkmann wrote:
> To answer your question: physmem could rearrange the memory to make it
> aligned better.  But currently it doesn't do that.  And I doubt it is
> practical to do that all the time, esp on hardware only supporting 4KB
> pages, and assuming a pager that pages memory as individual 4KB
> frames.  Also, consider shared pages: in that case the load address
> will be different across tasks.

If the tasks have the restriction that pages must be aligned, this 
shouldn't be a problem.  I just realised that this wouldn't work for the 
boot case, because the memory isn't alligned correctly in wortel, 
because laden (or grub?) put it in the wrong place.  This is a boot 
problem, which need not occur when the OS is up and running.

From a later mail:
> I have never thought much about how to do paging with arbitrary page
> sizes.  There are certain issues that arise, mainly that the pager
> must then make decisions when to break up a page and when not to

I'd think this is typically something that we don't want to do in 
physmem.  The reason tasks are self-paged is that they can make these 
kind of decisions by themselves, right?  If the pager we provide for 
posix programs doesn't do anything special, that's ok.  But if a pager 
wants to use it, it should be able to do so.

Thanks,
Bas

signature.asc
Description: OpenPGP digital signature