[jdom-interest] Internal DTD subset verification

[Elliotte Rusty Harold]

At 8:03 AM -0700 5/9/02, Philip Nelson wrote:


>In building systems where you are trying to maximize the number of 
>simultaneous
>users, this is not completely true, or false.  A slow IO time will mean that
>more documents will be loaded in memory at any point in time. 
>Depending on how
>much memory you have and how many users you need to support, this is a bad
>thing but there are ways to deal with it, add memory/swap space etc..  On the
>other hand, high IO time means that the cpu is free to do other more important
>things like service additional requests, increasing the number of simultaneous
>users.  A good thing.  Since cpu is much more difficult to manage than memory,
>I prefer to know that IO was not considered in the tests.  Also, in my
>experience, with all recent hardware, disk access is amazingly fast.  Just
>compare time copying a file to parsing the same file.
>

Let's make sure we're not comparing apples to oranges here. My claim 
is that any real world application that uses JDOM is going to spend 
so much time doing I/O, that document building time is insignificant. 
If you're trying to measure document build time exclusively, then you 
rightfully will try to eliminate the cost of I/O. However, the 
resulting benchmark really won't prove that we gain anything 
significant by optimizing document build time. If we reduce document 
build time to zero, I/O will still cost. We can't easily do anything 
about that. My claim is that the cost of I/O+SAX parsing is such that 
compromising correctness is not an acceptable trade-off for reducing 
JDOM tree construction time.

Also, please keep in mind, that although file access is an important 
and real-world use-case so is network access, and that's going to be 
even slower, often on the order of seconds. For instance, some of 
Dennis Sosnoski's tests are SOAP documents. In the real world these 
would almost certainly be served over a network connection. Even on 
the fastest LANs, the sheer overhead of setting up a single TCP/IP 
connection is likely to outweigh all other factors involved in 
document building.
-- 

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| Elliotte Rusty Harold | elharo at metalab.unc.edu | Writer/Programmer |
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