uncompress is slow for itanium server

[Hein van den Heuvel]

kenken,

Steven is of course correct, but cranky as ever. He's trying to provoke you to THINK about the data you are providing, what is happening or not happening on the systems and what might explain a difference.

Think about it... (ooops, now I did it :-)... you mentioned "3)disk io are almost the same 90%". So even is the CPU was inifinitely fast, it would seem the at best the speedup could be 10% more.... so it is the disk that defines the performance. 36MB/sec on the PA versus 27 MB/sec on the Itanium would explain it (assuming a hefty compression rate where the input IO throughput can be ignored).

Now I'll be the first to admit that there is a lot of handwaving in the above. 'disk busy' is precise, yet vague. It means there was something happening 90% of the time, but it does not mean that you might have been able to push the IO trough harder/smarter. And the actual (usermode) uncompress CPU usage is largely decoupled, hidden behind, the IO busyness.

That's why we all request more, and more precise data. How much CPU is being used ? (usermode, system). How fast is the IO subsystem... reading .. versus writing.

The 'writes' are more or less free, as long as they eventually find some time. The read speed defines whether the program has to wait for data to work on, or can keep on uncompressing, but the reads might be slowed down by the ongoing write work.

The most likely suspect (imho) is the characteristics of the IO systems provided (simple disk each?). But it could indeed still prove to be an CPU speed or porting issue. Only you can help us determine the more like cause / solution.

hope this helps some,
Hein van den Heuvel
Hvdh Performance Consulting.