Re: ¡@[*©U§£¶l¥ó*] Re: What File System supports Application XIP

["colin" <colin@realtek.com.tw>]

Hi Paulo,
Cramfs seems to support it now.
At the beginning, I also think it's impossible to support Application XIP in
Cramfs.
http://www.denx.de/twiki/publish/DULG/ConfigureLinuxForXIP.html

Regards,
Colin


----- Original Message ----- 
From: "Paulo Marques" <pmarques@grupopie.com>
To: "colin" <colin@realtek.com.tw>
Cc: <linux-kernel@vger.kernel.org>
Sent: Thursday, September 09, 2004 5:19 PM
Subject: ¡@[*©U§£¶l¥ó*] Re: What File System supports Application XIP


> colin wrote:
> >
> > Hi there,
> > We are developing embedded Linux system. Performance is our
consideration.
> > We hope some applications can run as fast as possible,
> > and are think if they can be put in a filesystem image, which resides in
> > RAM, and run in XIP (eXecute In Place)  manners.
> > I know that Cramfs has supported Application XIP. Is there any other FS
that
> > also supports it? Ramdisk? Ramfs? Romfs?
>
> Obvisously cramfs can not support XIP, because the "in-place" image
> is compressed (unless you have a processor that can execute compressed
> code :)
>
> AFAIK only tmpfs supports XIP because it works on a higher level
> without using block devices underneath. Ramdisks are simply RAM
> block devices that behave like any other block device.
>
> You can have a compressed image in flash (for instance), decompress
> everything into a tmpfs and execute from there.
>
> I'm not sure, however, that this will be such a performance gain.
>
> If you use cramfs (for instance) then the kernel will uncompress
> and run only the pages that are needed, and they will be cached in
> page cache so that they will be available again when needed. This
> way you only waste the RAM you actually need, and can still drop
> old pages if the application needs more RAM.
>
> Just my two cents,
>
> -- 
> Paulo Marques - www.grupopie.com
>
> To err is human, but to really foul things up requires a computer.
> Farmers' Almanac, 1978
>