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SubjectRe: large Ramdisks
Date
>From: "Christopher E. Brown" <cbrown@denalics.net>
>Date: Thu, 26 Aug 1999 16:30:19 -0800 (AKDT)
>Subject: Re: large Ramdisks
>
>On Thu, 26 Aug 1999, Patrick Bauer wrote:>
>
>>
>> Not sure if it is possible to create a large filesystem in memory... a
>> ramdisk... of size 64 mb... or 128 mb... i'm not sure why creating a
>> ramdisk of this size wouldn't be possible to achieve... i'd like to use
>> this large ramdisk after linux on disk has been booted..
>>
>> >From the info i've read... it seems like the size limit of a ramdisk
>can
>> only be 4 mb..
>
>
> RTFM ramsidk_size=

That's with a bootloader. You can do it without one by twiddling
drivers/block/rd.c and this guy...

int rd_size = 4096; /* Size of the RAM disks */


which is in kilobytes, and a lower reference to it further down in the
same file. The comments on this in the source seem to date to when
RAMdisks didn't grow, as do the kernel boot messages, in that the sizes of
the RAMdisks are not noted to be *maximums*. If I could find a global
variable for total RAM I'd make that value, rd_size, some large percentage
of total actual RAM. The sysinfo struct perhaps?

After twiddling the above you can get a whole small distro or "root
partition" on a ramdisk by compressing, say, 40 meg of mostly empty ext2
space onto a root floppy, and then copying a small partition into / after
booting from floppy. With your whole world in RAM a few things seem a bit
snappier, but no big win really. Empty ext2 gzips about 1000:1 .

Rick Hohensee
/*1 bye (Linux _exit)
void _exit(int status); _exit is to diff it from libc
*/
_syscall1(byte, _exit, byte, ds[dsl]);
ATOM_(bye)
_exit(ds[dsl] );
/* we never get here */




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