linux-kernel - What is the limit size of tmpfs /dev/shm ?

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Date:	Wed, 06 Feb 2008 15:54:06 +0100
From:	Tomasz Chmielewski <mangoo@...g.org>
To:	LKML <linux-kernel@...r.kernel.org>,
	Mika Lawando <rzryyvzy@...shmail.net>
Subject: What is the limit size of tmpfs /dev/shm ? 

> Hello Kernel Users,
> 
> is there a size limit for tmpfs for the /dev/shm filesystem?
> Normally its default size is set to 2 GB. Is it possible to create a 2 
> TB (Terrabyte) filesystem with tmpfs?
> Or is there a maximum size defined in the linux kernel?

Depends on your arch.

If it's 32 bit, it's limited to 16TB:

# mount -o size=16383G -t tmpfs tmpfs /mnt/2
# df -h
(...)
tmpfs                  16T     0   16T   0% /mnt/2

# umount /mnt/2

# mount -o size=16385G -t tmpfs tmpfs /mnt/2
# df -h
(...)
tmpfs                 1.0G     0  1.0G   0% /mnt/2


So 16384G would mean the same as 0.


If you're 64 bit, you need to have really loads of storage and/or RAM to 
accumulate 16EB:

# mount -t tmpfs -o size=171798691839G tmpfs /mnt/2
# df -h
(...)
tmpfs                  16E     0   16E   0% /mnt/2


-- 
Tomasz Chmielewski
http://lists.wpkg.org
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