Re: Research using L4Hurd

[Niels Möller]

address@hidden writes:

>       - we get away from the monolithic kernel design model, which
>         requires lots of data structure locking, to a more
>         component-based model with less locking but more IPC.

The componentization means that you replace kernel-internal interfaces
with explicit ipc interfaces. But the things that communicate over
such an interface typically didn't share a lot of datastructures from
the start, so there's not much locking you can get rid of there.

Using a microkernel doesn't necessarily reduce the need for locking.
For instance Hurd file servers are heavily threaded (one thread for
each open file), and uses mutex locks and the like to syncronize
access to shared data structures. I think needs for locking is comes
with multi-threading, no matter if you do it in the kernel or in user
proceses.

It might be possible to write servers in a more select-loopish
fashion, without multithreading, but that's not the recommended way to
do it on the Hurd, and I'm afraid it will be even more unnatural when
moving to L4 and its syncronous ipc.

/Niels