Throughput Degradation with 4GB Kernel

Partha Narayanan (partha@us.ibm.com)
Mon, 21 Jan 2002 18:04:50 -0600


Here are some VolanoMark results that show throughput
differences for 1GB and 4GB kernel build options.

This test runs in loopback mode, with no disk activity,
so the 4GB degradation should not be related to bounce
buffers.

A time based profile did not provide any insight into
why the 4GB kernel on a 4-way degrades. We will get a
a kernprof acg for both the 1GB and 4GB kernels.

This degradation was unexpected.
Any ideas on what may be causing this degradation ?

VolanoMark 2.1.2 10/100 loopback test,
8-way 700MHZ Pentium III,
IBM JVM 1.3. (build cx 130 -20010626)
Throughput in msg/sec

Kernel UP 4-way 8-way
======= ===== ===== ======
2.4.14 1GB 11024 17565 13734
2.4.14 4GB 11060 13378 13030
-----------------------------------------------

2.4.16 1GB 11064 16292 11840
2.4.16 4GB 11105 12605 9434
-----------------------------------------------

2.4.17 1GB 11005 15894 11595
2.4.17 4GB 11057 12754 9363
-----------------------------------------------

Partha Narayanan
partha@us.ibm.com

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