Re: Interprocess shared memory .... but file backed?

Richard B. Johnson
2002-03-08T15:52:27Z

On Fri, 8 Mar 2002, Christopher Quinn wrote:

> Hello,
>
> I know that a combination of mmap/shmem can be used to
> achieve interprocess shared memory (notably Ralf
> Engelschall's MM library).
> However as far as I can tell this is anonymous memory only.
> Are there any options if one initially maps a disk file via
> mmap (in particular MAP_PRIVATE) for sharing that vm, such
> that any access by a member of the sharing process group
> will fault in the relevant file data page after which writes
> to it are seen by all?

Hmmm. You want MAP_SHARED, but you insist upon using MAP_PRIVATE?
MAP_SHARED makes your mmapped pages visible to all, complete
with any updates by any or all tasks accessing it.

Cheers,
Dick Johnson

Penguin : Linux version 2.4.18 on an i686 machine (799.53 BogoMips).

Bill Gates? Who?