In article <1992Aug12.215042.5114@murdoch.acc.Virginia.EDU> lfoard@Turing.ORG (Lawrence C. Foard) writes:
>Is there any soft of project underway to implement memory mapped files
>in Linux? It seems that the shared library code is pretty close except
>that it doesn't support writting pages back to the library file.
>
>Has anyone looked into what would be involved?
Ideally, some one will implement something along the lines of a
vnode based vm system, where each virtual memory object has a mapping
and certain characteristics associated with it.
That mapping could be to a file, to a device, etc. Ideally, a file mapping
would be a mapping to blocks as specified by the file's bmap, with those
blocks shared with buffercache. Shared libararies / mmap / sysV
shared memory semmantics could be implemented on top of this
internal structure, quite easily.
very similiar to what MACH uses.
>Along with this is there any reason to keep the 4giga byte total
>limit for processes rather than having seperate page tables for
>each process?
Not 4G per process. You still want room for kernel space in the
same page table, so you can keep most of the same code in place
for kernel<>user space transfers, with kernel and user space in
different x86 segments. Linus has something going with
> 3G per process, with the remainder allocated to the kernel -
--
Microsoft is responsible for propogating the evils it calls DOS and Windows,
IBM for AIX (appropriately called Aches by those having to administer it), but neither is as bad as AT&T. Boycott AT&T, and let them know how you feel.
