From: P.H.Welch (P.H.Welch_at_email.domain.hidden)
Date: 2000-09-22 17:56:28
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From: Ruth Ivimey-Cook <Ruth.Ivimey-Cook_at_ivimey.org>
Subject: Re: "No aliasing = no garbage collection"
In-Reply-To: <E13cRxu-0004sG-00_at_myrtle.ukc.ac.uk>
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At 13:30 22/09/00 +0100, you wrote:
>} In my opinion, garbage collection is an efficiency mechanism.
>} Conclusion (assuming I remembered correctly that the proof can be done):
>} if you are not bothered with performance, use a garbage collector,
>} and save on memory budget, use virtual memory as well.
>}
>} if you are bothered with performance, buy twice as much memory, and
>} do not use a garbage collector, nor virtual memory. Simply, use
>} enough memory.
>Yes, I agree...
>
>The temptation to attach every bell and whistle is a strong one.
>But that problem becomes an opportunity when you remember that
>implies that the niche of clean, understandable simplicity is
>almost unoccupied.
>Larry
I am slightly worried by this view. The experience of many ARM customers,
working in the embedded space, is that memory is definitely not cheap. The
reasons are:
1. What memory you have must be on-chip with the processor, which mostly
limits it to small quantities of SRAM and slightly larger quantities of ROM
or EPROM.
2. The cost of many consumer items is a multiple of the manufacturing cost.
That is, if it costs $5 to build, it costs $50 at the retailer (and that is
perhaps understating the multiple). Consequently, adding a $10 DRAM to a
design is not an option -- it would add $100 to the selling price.
3. Items like mobile phones typically have huge memory requirements --
3-5MB ROMS is not unusual, and RAM is also needed in large quantity. And
yet if you look inside these devices you find only a couple of chips.
Doubling the physical space required for memory is not possible -- it
doesn't fit.
I believe there should be a garbage collection scheme added to occam. It is
a great language for many things, but it is let down in areas which people
care about intensely.
Regards,
Ruth
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