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Re: OCaml is broken
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Date: -- (:)
From: Yaron Minsky <yminsky@g...>
Subject: Re: [***SPAM*** Score/Req: 10.1/8.0] Re: [Caml-list] Re: OCaml is broken
On Sun, Dec 20, 2009 at 7:21 AM, Erik Rigtorp <erik@rigtorp.com> wrote:

> The first step for OCaml would be to be able to run multiple
> communicating instances of the runtime bound to one core each in one
> process and have them communicate via lock free queues.


We've done some experiments in this direction at Jane Street.  On Linux,
we've been able to get fast enough IPC channels for our purposes that
slamming things into the same memory space has not in the end been
necessary.  (There is I agree some pain associated with running multiple
runtimes in the same process.  If you're interested, contact me off-list and
I can try to get you some of the details of what we ran into.)

But have you tried using shared-memory segments for communicating between
different processes?  You say the latencies are too high, but do you have
any measurements you could share? Have you tried queues using shared memory
segments, in particular?  Inter-thread communication has latency as well,
and the performance issues depend on lots of things, OS and hardware
platform included.  It would help in understanding the tradeoffs.

As we go to higher-and-higher numbers of cores, I suspect that
message-passing solutions are likely to scale better than shared memory, so
I'm not so sure that OCaml is on the wrong path here.  I think that most of
the work that's needed is going to come in the form of libraries, with only
a little work in the compiler and the runtime.  Given that, I think this is
an issue for the community to solve, not INRIA.

y