Default performance on Sun T5440

[jeff.lloyd at algorithmics.com]

Hi,

 

I just ran my application on a new box from Sun and found immediate
debilitating java performance by default.

 

System Configuration:  Sun Microsystems  sun4v T5440

Memory size: 65248 Megabytes

 

================================ Virtual CPUs
================================

 

 

CPU ID Frequency Implementation         Status

------ --------- ---------------------- -------

0      1164 MHz  SUNW,UltraSPARC-T2+    on-line  

1      1164 MHz  SUNW,UltraSPARC-T2+    on-line  

...

254    1164 MHz  SUNW,UltraSPARC-T2+    on-line  

255    1164 MHz  SUNW,UltraSPARC-T2+    on-line  

 

four UltraSPARC T2 Plus processors per system, 256 threads; 1.2 GHz

 

The default java behaviour is to use all 256 virtual processors for
garbage collection, and even for small ParNew collections the system was
being hammered.  The cpu load reported by prstat was 150 during
too-frequent and long-running YG garbage collections.  I had to specify
-XX:ParallelGCThreads=8 to bring the gc under control.

 

I just wanted to let you know that the default gc behaviour for Sun's
JVM on Sun's hardware produces undesirable results.  I don't think most
people will know how to diagnose or fix this problem.

 

Jeff

 


 
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