Re: Data queue space

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

M
Hello James,

You wrote:
>One last concern though, and with the current speed of machines it may
>be moot, but what is the performance curve on a data queue?  I
>understand they get slower the bigger they get.

I should take my own advice and read all the replies before replying however 
SOMEBODY 
changed the subject line and I thought I had read everything ...

KEYED data queues do get slower the more entries they contain.  The sort 
algorithm used 
by data queues is still an Order n squared sort.  I don't believe IBM have 
changed it 
because user queues, which provide a similar fuction, use a different and 
faster 
algorithm.

However, the performance penalty is paid at different times.  On CISC systems 
(who is 
STILL using one of those?  Time to move, people!!!) the sort is done when 
entries are 
enqueued therefore the sending process suffers the performance penalty.  On 
RISC systems 
the sort occurs on the dequeue and the receiving process suffers.  
Significantly so 
sometimes but not worth worring about until the number of entries is in the 
hundreds.

Non-keyed queues don't have the problem.

Don't try this at home:  Fill a keyed data queue with thousands of entries, 
then start a 
process to receive the entries.  See how long it takes to get the first entry 
.....

Regards,
Simon Coulter.

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