tmpfs size option not working

[Rob Landley]

On Thursday 05 January 2006 09:58, Mike Frysinger wrote:
> On Thursday 05 January 2006 10:15, Julien MARBACH wrote:
> > But I find confusing that the "tmpfs" name is sometimes used to meen
> > ramfs and sometimes for tmpfs itself. For example when I do a $
> > cat /proc/filesystems (wich tells me what fs are supported by my kernel)
> > tmpfs is listed wether CONFIG_SHMEM is set or not in my kernel config.
> > So when CONFIG_SHMEM is not set tmpfs stand for ramfs, and when
> > CONFIG_SHMEM is set, tmpfs stands for _real_ tmpfs.
> > This could be confusing!
>
> that is weird ... it's been my experience that if you have tmpfs disabled
> in the kernel, then tmpfs wont show up ... in fact, we have code in the
> Gentoo init system to handle this case because when we assumed tmpfs
> existed, it broke a few users' boxes ...

When CONFIG_SHMEM is set, tmpfs is hardwired into the kernel to implement 
system V shared memory.  There's a seperate config entry, CONFIG_TMPFS, that 
enables the userspace controls (allowing additional tmpfs mounts to occur 
from userspace).

It can be confusing.  I bumped into this in October:
http://groups.google.com/group/linux.kernel/browse_frm/thread/4a1ad11d0f556521/d8f34dfdc6620d5e?tvc=1

I believe the reason they want to use tmpfs instead of ramfs for shm is that 
tmpfs is swap backed and ramfs is pinned and unswappable.

Rob
-- 
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I do not think it means what you think it means.