From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] vfork and paging
From: rog@vitanuova.com
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Message-Id: <20011002140038.18B9D1998A@mail.cse.psu.edu>
Date: Tue,  2 Oct 2001 15:12:49 +0100
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> I always thought this made sense too. I always wondered though why Alef
> had threads. And who's using the thread library?

that's a good point.

even when OS processes are cheap, they're still not as cheap as
longjmp()...  hence the thread library, presumably.

it's interesting to see that despite the distinction between threads
and procs in the thread library, the API is the same - the same
communication and synchronisation primitives work between all of them.

internally, Inferno also has the same distinction between threads and
processes ("progs and kprocs"), although the distinction isn't visible
at the API level.  simple threads are used until a call is encountered
that may block on an external event, in which case a kproc is summoned
for the operation.

a channel communication doesn't count as an external event, so one can
write quite sophisticated multi-process programs quite cheaply.
(it's a bit more awkward & error prone in C than in Limbo though
as it doesn't have the language support)

  rog.