emm and fd migration

Louis-D. Dubeau (ldd@step.polymtl.ca)
Tue, 11 Jul 1995 14:10:26 -0400

I think a saw somewhere that somebody tried to integrate file
descriptor migration to the kernel (like the I_SENDFD ioctl for
streams). Have I dreamed or has anybody actually worked on this?

The reason I ask this is that I'd like to implement external memory
managers in Linux. My plan is not to get the default memory manager
out of the kernel (not right now anyway) but rather to permit the use
of emms for DBMSes and other data intensive applications.

Here is an outline of what I have in head:

- the server creates the object with a syscall that returns a fd
the created file uses a special mmap operator
- the client gets the object from the server: the fd must
be send to the client
- the client mmaps the object using the fd it received
- faults and such are send to the server through ipc
- the results are returned to the kernel by ipc (????)

I'm not sure that the kernel supports fd transfers between processes.
Is the multithreading support (through clone) robust enough? (An
external mem manager needs threads.)