Data transfer mechanisms

[Lluís Vilanova]

Hi,

I'd like to compare the performance of two different synchronous data transfer
mechanisms:

* Copies
* Page maps / unmaps

For the second one, it looks like I can use the streammap example
(pkg/examples/libs/l4re/streammap), although I'm lacking a mechanism to unmap
the page before returning control to the client. It would also be nice to be
able to pass the server a read-only region.

For the first one, I've only found the use of multiple send/recv operations
through the limited amount of data available on the message registers. There is
a "Gen_string" class in the "ipc_stream" header, which looks like it could
support offline string transfers, but it's disabled at compile time and I could
not find the actual code in fiasco that handles these transfers.


Thanks,
  Lluis

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