linux ramdisk ram disk

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From - Mon Dec 11 07:14:32 2000
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From: Peter Pointner <pn01@wuzel.de>
Newsgroups: comp.os.linux.development.system
Subject: Re: ramdisk: how much mem do they use?
Date: 9 Dec 2000 19:13:46 +0100
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Jerome Corre <jerome_corre@my-deja.com> wrote:
>  hi

> I have 32Mb of ram on my linuxbox, I sometime use ramdisk (/dev/ram0 or
> /dev/ram1) to store small filesystem, prepare a bootdisk or when my
> system boot usimg initrd.
> I would like to know if it is possible to know how much memory the
> ramdisk are using. I suppose that they don't all use 4Mb as there are 16
> ramdisk i can use and I only have 32 Mb of ram. How can I found out how
> much memory they use? and if I don't need what is left on one of them
> after i unmount it how can I free the memory a ramdisk use?

The ramdisks use ram only as needed. Initially your 16 ramdisks use no
ram, or almost no (there are probably some data structrures in the kernel.
If you use them, you normally create a file system on them. so if you
create a 1 MByte ext2 file system on /dev/ram0, it uses 1 MByte of ram.
AFAIK the 4 MBytes are only a (configurable) upper limit.

If you want to free the memory, you can do that with the tool freeramdisk,
which seems to do some ioctl on the ramdisk device.

Peter

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