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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Multitasking and containers
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Date: Tue, 28 Nov 2006 09:50:03 +0100
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Date: 2006-11-28T09:50:03+01:00
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On Tue, 28 Nov 2006 02:19:55 GMT, Matthew Heaney wrote:

> "Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk> writes:
> 
>> Actually, I think Dmitry's view is largely valid in practice, if
>> somewhat extreme.
> 
> But we were talking specifically about using a protected object to implement a
> multiple readers schema vs. using a protected object to implement a Hoare-style
> monitor.  Because reads must by synchronized, the standard container library
> requires a monitor-style synchronization scheme.
> 
> The OP made the argument that this isn't very efficient, and Dmitry responded
> by saying, "well of course systems require custom hand-made solutions." But the
> premise is all wrong, so what Dmitry said is irrelevant.  The OP (not Dmitry)
> seems to be confused (he was asking the question, after all) about the
> difference between a mutex and a monitor.  He (the OP) probably doesn't
> understand that monitor-type synchronization executes on the current thread, so
> there's no context switch, and so there's no efficiency loss.

I read OP question very differently. He said (let Maciej correct me):

1. That accessing a mutable operation disguised as a protected object's
function were wrong.

2. Using a protected object's procedure/entry would kill concurrency by
serialization of the action to undertake.

Both statements are evidently true.

My comments considered possible solutions *provided* that 2 were really a
problem, because as Jeffrey rightly pointed out, the loss of performance
could be actually minor. But that depends. It is easy to imagine a
situation (massively parallel computing with shared memory) where the loss
could be huge.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de