Re: [PATCH] System V Shared memory interface

[Roland McGrath]

Can you give concise answers to these questions?

1. What facility does your new RPC interface provide
   over using the normal filesystem interfaces with
   some convention of fixed-length file names for shm keys?

2. What functionality does your shmfs provide over a normal filesystem?


When proposing any new interface, or any new server that does something
very similar to an existing server, I think you need to first justify why
the current facilities don't suffice and explore how they might be tweaked
or extended slightly to cover the need. 


At some point in the not too distant past I went over the shm interfaces in
contemplation of a Hurd implementation.  I don't really recall anything
specific about it, but my vague recollection is that I concluded there was
just one new interface or quirk of functionality that would be required to
meet the basic shm semantics (leaving aside the pid reporting and all
that).  Maybe shm lets you continue to open a file after it's been deleted
but still has live users?  Something like that.  

I am strongly in favor of an approach where using any vanilla filesystem
directory for /var/run/sysvshm works in a pinch (and maybe loses on some
obscure point of shm behavior).