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To: "J . A . Magallon" <jamagallon@able.es>
Cc: "H . Peter Anvin" <hpa@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: [patch] tmpfs for 2.4.1
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	<m3lmrqrspv.fsf@linux.local> <95csna$vb6$1@cesium.transmeta.com>
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From: Christoph Rohland <cr@sap.com>
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"J . A . Magallon" <jamagallon@able.es> writes:

> I did not get the chance to deal too much with it, but apart from moving
> functionality from userspace (ipcs) to kernel (ls), what were/could be the
> benefits of /dev/shm ?. Can you create a shared memory segment by simply
> creating a file there, or it is just a picture of what is in kernelspace?.

The most appealing thing to me was rm -f /dev/shm/.IPC* :-) So I
should make a patch to ipcrm to allow multiple segments (and
wildcards?).

You could not create SYSV shm segments with open, but you could delete
them with rm and list the with ls.

> First time I saw that I thought: what could happen if /dev/shm is shared
> in a cluster ? or, lets suppose that /dev/shm is a logical volume made by
> addition of some nfs mounted volumes, one of each node, so one piece of
> the shm fs is local and other remote...kinda DSM/NUMA...?

No, this was never possible. It was only a fs interface to local
kernel objects (and still is).

> (just too much marijuana late at night...)

Oh, you are allowed to dream ;-)

Greetings
                Christoph

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