Re: a 15 GB file on tmpfs

Erik Mouw
2005-07-20T14:44:45Z

On Wed, Jul 20, 2005 at 01:35:07PM +0000, Miquel van Smoorenburg wrote:
> In article <20050720132006.GI7050@harddisk-recovery.com>,
> Erik Mouw <erik@harddisk-recovery.com> wrote:
> >On Wed, Jul 20, 2005 at 02:16:36PM +0200, Bastiaan Naber wrote:
> >AFAIK you can't use a 15 GB tmpfs on i386 because large memory support
> >is basically a hack to support multiple 4GB memory spaces (some VM guru
> >correct me if I'm wrong).
>
> I'm no VM guru but I have a 32 bit machine here with 8 GB of
> memory and 8 GB of swap:
>
> # mount -t tmpfs -o size=$((12*1024*1024*1024)) tmpfs /mnt
> # df
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/sda1 19228276 1200132 17051396 7% /
> tmpfs 12582912 0 12582912 0% /mnt
>
> There you go, a 12 GB tmpfs. I haven't tried to create a 12 GB
> file on it, though, since this is a production machine and it
> needs the memory ..

I stand corrected.

> So yes that appears to work just fine.

The question is if it's a good idea to use a 15GB tmpfs on a 32 bit
i386 class machine. I guess a real 64 bit machine will be much faster
in handling suchs amounts of data simply because you don't have to go
through the hurdles needed to address such memory on i386.

Erik

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