WebSphere Performance IssueOn PowerPC / AIX

Question

We are seeing extremely poor performance on a WebSphere 6(JDK 1.6) system on PowerPC arch with AIX. We are using Dynatrace to pinpoint the sources. It appeared to point to significant slowness in low level JDK operations like classloading, sockets, file IO.

After some research we thought the problem may be JDK versions. So we updated the system to WebSphere 8.55 and JDK 1.7. Unfortunately the problem persists. We observe the following 2 characteristics:

• Frequently, the slowness is reported in Java low level functions.
• Dynatrace reports API CPU Time and API Execution Time.

Under Windows (same WebSphere and JDK version) we see the 2 times are fairly close. On the AIX system, the 2 values commonly differ by a factor of 3 to 4.

Here are some examples of observed issues:

• Almost 2 seconds to load a class
• Class copyMethods
• setObject On PreparedStatement calling socketRead?

Any thoughts? Is the problem AIX, PPC, IBM JDK, WebSphere???

Answer 1

I've seen dozens of Websphere 6/7/8.5 and now 9 instances running on the same PowerPC AIX without any problem.

If you really want to know what's happening under the hood, I'm afraid you're going to "get dirty" and try with the following tools:

1. Xtrace : the IBM JVM has this amazing tool that allows us to trace methods. You can try to isolate the "hot points" that are impacting the performance.

https://www.ibm.com/docs/en/sdk-java-technology/7.1?topic=tjaj-using-method-trace-1

2. Xcheck:jni : you can trace at a JNI level

https://www.ibm.com/docs/en/sdk-java-technology/8?topic=jni-debugging

If the problem is at a JVM level, then your problem is not Websphere, so stop testing the whole server. I recommend you to test a simple main class that loads one or more classes. If you're able to reproduce the problem in a more trivial test, it's going to cost you less effort to get to whatever is causing that.