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From dean gaudet <dean-list-apr-...@arctic.org>
Subject Re: Shared Memory in APR
Date Sat, 07 Jul 2001 17:57:06 GMT
On Wed, 4 Jul 2001 rbb@covalent.net wrote:

> On Wed, 4 Jul 2001, Ian Holsman wrote:
>
> > I'm looking at the shared memory functions (in unix), and am struggling
> > to find out how one can attach to
> > a shared memory segment already created by another process.
>
> Currently you can't, because MM doesn't really support it.  We need to
> re-write the shared memory code, but it doesn't make a lot of sense to do
> that until the SMS stuff calms down.

MM doesn't support it because it's non-portable.

consider unix without sysvshm, posix shm, etc., but with anonymous shared
mmap().  anon shared mmap() doesn't require file backing -- it can live in
memory with no need to ever sync to disk.  to support attach by other
(arbitrary) processes you need to have a backing file (handle for mmap()).
say bye bye to performance.

isn't this the case with various BSD-based systems?

-dean


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