jffs2 compression question

jffs2 compression question

[Brian T.]

Hi,

I have jffs2 running on a 2.4.20 kernel custom Embedded box with 16MB ROM
(Intel flash) and 32MB RAM.  The file system is about 52% full, and has
about 22MB of free RAM.  When I copy 4 ~1.6MB programs over to the ROMFS I
loose about 3MB of space with compression.  The system however also uses
another ~3MB RAM once the files are done being copied.  My question is, when
does (if ever) that 3MB RAM get freed up?  If I delete the files I just
copied, the RAM appears to be freed up.   If I reboot the unit, the RAM gets
reset back to the original 22MB RAM free.

Thanks for any insite.

-Brian

Re: jffs2 compression question

[Russ Dill]

> I have jffs2 running on a 2.4.20 kernel custom Embedded box with 16MB ROM
> (Intel flash) and 32MB RAM.  The file system is about 52% full, and has
> about 22MB of free RAM.  When I copy 4 ~1.6MB programs over to the ROMFS I
> loose about 3MB of space with compression.  The system however also uses
> another ~3MB RAM once the files are done being copied.  My question is, when
> does (if ever) that 3MB RAM get freed up?  If I delete the files I just
> copied, the RAM appears to be freed up.   If I reboot the unit, the RAM gets
> reset back to the original 22MB RAM free.

linux tries not to let any RAM go to waste, so if there is free ram, it
uses it for caches and buffers. If you were to read these files again,
it would happen quickly because they are in RAM. If more RAM is needed
for other things, then less caches and buffers are used (see
/proc/meminfo for more info)

> Thanks for any insite.

don't worry, everything is working rite.

Re: jffs2 compression question

[Thomas Gleixner]

On Thursday 17 April 2003 21:10, Brian T. wrote:
> Hi,
>
> I have jffs2 running on a 2.4.20 kernel custom Embedded box with 16MB ROM
> (Intel flash) and 32MB RAM.  The file system is about 52% full, and has
> about 22MB of free RAM.  When I copy 4 ~1.6MB programs over to the ROMFS I
> loose about 3MB of space with compression.  The system however also uses
> another ~3MB RAM once the files are done being copied.  My question is,
> when does (if ever) that 3MB RAM get freed up?  If I delete the files I
> just copied, the RAM appears to be freed up.   If I reboot the unit, the
> RAM gets reset back to the original 22MB RAM free.

Have you taken the +/- buffers/cache into account ?

-- 
Thomas
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