WebSphere Application Server setup

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For our performance tests, we used the default asynchronous I/O mode for WebSphere Application Server.

Asynchronous I/O

By default, WebSphere® runs in asynchronous (async) I/O (AIO) mode because the libibmaio.so is included in the WebSphere directory structure. To disable this feature, or to run in "non-AIO" mode, the file was renamed and removed from the WebSphere directory structure. This package provides facilities for performing AIO for both files and sockets. For example:
  • mv libibmaio.so /tmp/libibmaio.so_ORG
  • mv libibmaiodbg.so /tmp/libibmaiodbg.so_ORG

One of the major contributors to enhanced performance with AIO is in the form of saved context switches and thread scheduling due to the fact that threads themselves handle their own I/O with our fully AIO model. In our runs we did not see a big change in performance when running with or without AIO. The reason might be that in our setup we do not stress this feature enough.