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Re: Shared-Memory for the Hurd?


From: Marcus Brinkmann
Subject: Re: Shared-Memory for the Hurd?
Date: Fri, 5 Jan 2001 16:41:42 +0100
User-agent: Mutt/1.1.4i

On Fri, Dec 01, 2000 at 04:01:47AM +0100, Farid Hajji wrote:
> 5.) fullsized translator, providing pseudo-filesystem:
> 
>   * each shm-segment is represented by a pseudo-file managed by a
>     fullsized translator settrans on e.g. /shm. The translator manages
>     vm_allocate()ed pages just like in 3.) and 4.), mapping them to
>     the pseudo-files [that is: shm-segment 34343 is mapped to /shm/34343].

Yes, this is a way to go. This could be a derivative of tmpfs, providing
only a flat directory (Roland suggested /var/run/sysvshm) and only accepts
certain file names coresponding to a key_t != 0 "with a funny behaviour
about unlinking open files so the SHM_RMID behaviour is right." (Roland).

Farid, this is an excellent medium sized project to dive into the Hurd
inners. Are you still interested in implementing this?

> Notes:
>   * shm-segments are visible as plain [pseudo-] files and could also
>     be mmap()-ed, or read()/write()... from other processes that have
>     enough permissions.

Yes, mmap() would be ideal.

> 5. same as in 4, but much more harder to implement, since there
>    is no good template/hello for a full filesystem translator in
>    the Hurd right now (besides full-blown ext2, ufs).
>    -> What about /procfs translator? Someone wrote such a beast,
>       but it is not in CVS. Where to get it please?

Well, tmpfs should be a good start. It isn't functional currently and not
tested, but there are only small changes necessary to make it work (coming
soon). tmpfs uses virtual memory to store the files.

Thanks,
Marcus

-- 
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de



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