Question

I have MQ server 7.1 running in machine1. I have a java app running in machine 2, that uses JMS to write messages to a queue in machine 1. The java app handles hundreds of messages per second (data coming from else where). Currently it takes about 100ms for 200 text messages (average size 600 bytes) or 2000 messages per second to write messages to the queue. Is this reasonable performance. What are some of the things that one can do to improve the performance further. i.e. faster?

Answer 1

There are a number of detailed recommendations available in the WebSphere MQ Performance Reports. These are published as SupportPacs. If you start at the SupportPac landing page, the ones you want are all named MPxx and are available per-platform and per-version.

As you will see from the SupportPacs, WMQ out of the box is tuned for a balance of speed and reliability across a wide variation of message sizes and types. There is considerable latitude for tuning through configuration and through design/architecture.

From the configuration perspective, there are buffers for persistent and non-persistent messages, an option to reduce disk write integrity from triple-write to single-write, tuning of log file sizes and numbers, connection multiplexing, etc., etc. You may infer from this that the more the QMgr is tuned to specific traffic characteristics, the faster you can get it to go. The flip side of this is that a QMgr tuned that tightly will tend to react badly if a new type of traffic shows up that is outside the tuning specifications.

I have also seen tremendous performance improvement allocating the WMQ filesystems to separate spindles. When a persistent message is written, it goes both to queue files and to log files. If both of those filesystems are in contention for the same disk read/write heads, this can degrade performance. This is why WMQ can sometimes run slower on a high-performance laptop than on a virtual machine or server of approximately the same size. If the laptop has physical spinning disk where the WMQ filesystems are both allocated and the server has SAN, there’s no comparison.

From a design standpoint, much performance can be gained from parallelism. The Performance reports show that adding more client connections significantly improves performance, up to a point where it then levels off and eventually begins to decline. Fortunately, the top number of clients before it falls off is VERY large and the web app server typically bogs down before WMQ does, just from the number of Java threads required.

Another implementation detail that can make a big difference is the commit interval. If the app is such that many messages can be put or got at a time, doing so improves performance. A persistent message under syncpoint doesn’t need to be flushed to disk until the COMMIT occurs. Writing multiple messages in a single unit of work allows WMQ to return control to the program faster, buffer the writes and then optimize them much more efficiently than writing one message at a time.

The Of Mice and Elephants article contains additional in-depth discussion of tuning options. It is part of the developerWorks Mission:Messaging series which contains some other articles which also touch on tuning.