ramfs/tmpfs/shmfs doubt

ramfs/tmpfs/shmfs doubt

[Anil Kumar]

Hello All,

   I have  a   doubt regarding use Of ramfs .In which cases should i
use ramfs/shmfs/tmpfs/ramdisk and how page cache is used in these cases?

   On my board i have 8 MB RAM and a Flash (to store Kernal and
Application code and persistent Application Data). Also i have no additional 
device to use it as a swap.So if for swap i have to use a part of
RAM(Compressed Swap suggested on this mailing list earlier).

   I am planning to create a file system at boot time in RAM and download
application binaries to that and run.RAM is limited so my  requirement is 
that i do not want to have two copies of data in the RAM (One in File
System i create and other one in Page Cache ).

  What is the best available mechanism i should follow?
   (Can  i use ramfs/tmpfs to solve the above problem?)

  Can i run a linux kernel disabling swapping (In my case no
 additional device for swap is available) ?

 Thanks a lot,  
 Anil


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/

Re: ramfs/tmpfs/shmfs doubt

[Jonathan Morton]

>    I am planning to create a file system at boot time in RAM and download
>application binaries to that and run.RAM is limited so my  requirement is
>that i do not want to have two copies of data in the RAM (One in File
>System i create and other one in Page Cache ).

Tmpfs and shmfs are two names for the same thing (the latter is 
deprecated), and I believe it will do what you want.  It exists in 
the pagecache, and I understand this is routinely mapped into process 
space for execution.

Ramfs creates a whole new section of memory and treats it as a block 
device, and the pagecache is used in addition to that.  This is not 
what you want, and I understand ramfs itself is discouraged since 
tmpfs is now in widespread use.  Cramfs is still useful as it uses 
compression on the "block device".

>   Can i run a linux kernel disabling swapping (In my case no
>  additional device for swap is available) ?

Certainly.  Simply don't provide a swap device or run swapon.  It'll 
work just fine until you run out of RAM, in which case you'd be 
screwed in any case.  :o)  I naturally assume you'll be running quite 
lean and tightly-controlled apps on that.

-- 
--------------------------------------------------------------
from:     Jonathan "Chromatix" Morton
mail:     chromi@chromatix.demon.co.uk
website:  http://www.chromatix.uklinux.net/
geekcode: GCS$/E dpu(!) s:- a21 C+++ UL++ P L+++ E W+ N- o? K? w--- O-- M++$
           V? PS PE- Y+ PGP++ t- 5- X- R !tv b++ DI+++ D G e+ h+ r++ y+(*)
tagline:  The key to knowledge is not to rely on people to teach you it.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/