[Q] MMU & VM

[Q] MMU & VM

[Graffiti]

Hi all,

	Before I ask my question, just to let you know, yes, I did look
for information on the web and various books to see if I could answer
this myself.  Alas, no luck.  Anyways, here goes:

	Just how does an MMU work, and why do we need it to implement
virtual memory instead of handling it all in the kernel?

	I've found quite a few texts on how VM works, but never why we
need an MMU or what an MMU does.

	Can anyone recommend a good book on this?

-- DN (Learning 68000 asm as we speak.  Now, for the Mac SE specs...)
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Re: [Q] MMU & VM

[Rik van Riel]

On Fri, 4 Sep 1998, Graffiti wrote:

> 	Just how does an MMU work, and why do we need it to implement
> virtual memory instead of handling it all in the kernel?
> 	I've found quite a few texts on how VM works, but never why we
> need an MMU or what an MMU does.
> 
> 	Can anyone recommend a good book on this?

Well, there's Tanenbaum's "Modern Operating Systems".

There's also a nice VM tutorial from CNE/CMU(?), which
is linked to from the Linux-MM homepage, VM Links.

http://www.phys.uu.nl/~riel/mm-patch/

Rik.

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RE: [Q] MMU & VM

[estafford]

I was compiling the 2.1.122 kernel on an Alpha box (LX164) and had this error
pop up.  Sounds like something you guys might recognize:

page_alloc.c: In function `__free_page':
page_alloc.c:169: internal error--unrecognizable insn:
(jump_insn 274 270 275 (return) -1 (nil)
    (nil))
gcc: Internal compiler error: program cc1 got fatal signal 6
make[2]: *** [page_alloc.o] Error 1
make[1]: *** [first_rule] Error 2
make: *** [_dir_mm] Error 2
{standard input}: Assembler messages:
{standard input}:178: Warning: Missing .end or .bend at end of file
cpp: output pipe has been closed

If you need more info, please just say the word.  Thanks!

----------------------------------
Ed Stafford
iXL Hosting Programming Engineer
E-Mail: estafford@ixl.com
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Re: [Q] MMU & VM

[Zlatko Calusic]

estafford@ixl.com writes:

> I was compiling the 2.1.122 kernel on an Alpha box (LX164) and had this error
> pop up.  Sounds like something you guys might recognize:
> 
> page_alloc.c: In function `__free_page':
> page_alloc.c:169: internal error--unrecognizable insn:
> (jump_insn 274 270 275 (return) -1 (nil)
>     (nil))
> gcc: Internal compiler error: program cc1 got fatal signal 6
> make[2]: *** [page_alloc.o] Error 1
> make[1]: *** [first_rule] Error 2
> make: *** [_dir_mm] Error 2
> {standard input}: Assembler messages:
> {standard input}:178: Warning: Missing .end or .bend at end of file
> cpp: output pipe has been closed
> 
> If you need more info, please just say the word.  Thanks!
> 

Something like that has already been reported and it looks like older
egcs compilers have trouble with __builtin_return_address construct.

Either update your egcs, or #define __builtin_return_address(x) (0)

Hope it helps.
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Posted by Zlatko Calusic           E-mail: <Zlatko.Calusic@CARNet.hr>
---------------------------------------------------------------------
Unix Wizard: Someone who can type `cat > /vmunix` and get away with it!
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