[colug-432] execute in-place

[Rick Troth]

I changed the subject so as to not be hijacking the conversation.

What forms of FS class storage are memory addressable?

Scott's original question made me think of this, and Matt's latest
response did so again.  I would have expected one difference between
MicroSD (or any "card" storage) and external SSD (or any "disk", or
anything "external") is memory addressability.  But it turns out that
even hard-wired memory is often wired differently from RAM or ROM.

On Sun, Mar 17, 2013 at 2:00 PM, Matt Simmons
<standalone.sysadmin at gmail.com> wrote:
 ...
> Well, so for the OS itself, yes. You get boot times of a few seconds,
> but once it's running, as you said, the OS loads from memory at the
> same speed as ever. The REAL magic is when you load up your
> applications. They open instantly. If you put %ProgramFiles% on solid
> state media, then everything in it will also load fast (except for any
> libraries living in system32).   ...

So there's a filesystem for mainframe Linux called XIP.  It's really
just a mount option on EXT2.  But you need your EXT2 in addressable
memory (ROM).

With the "xip" option, files are already in memory, so they're read
(or executed) by just pointing (or jumping or branching).  It's
particularly nifty when you have virtual machines sharing the chunk of
ROM where the filesystem resides.

TO MY SHOCK, I recently learned that hand-helds and smart phones
cannot use XIP.  I was told that even though flash is "memory", it is
not reachable by peek and poke.  Bummer.


-- 
-- R;   <><