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Connection scalability of Java virtual machines that are freely available now. Bigger numbers are better. All JVMs ran the same test on the same Intel hardware platform except for Apple MRJ 2.0, which ran on a Power Mac G3.
These seven Java virtual machines are the ones we recommend to our customers for running the VolanoChat product live on production
Web sites. The chart shows the VolanoMark 2.0 scores for seven Java VMs as the number of connections are increased. The number
of connections are shown across the bottom, with the throughput in messages per second shown on the left. The scores are shown
at up to 900 concurrent connections. Failed tests in the table are indicated by "
---" (no score shown).
Microsoft SDK 2.02 still stands alone as the only fast and scalable Java virtual machine. Our customers with the highest Web site traffic currently have no other viable choice for a JVM. I had to restart the JavaSoft JDK 1.1.6 virtual machine five times between tests in order to reach 900 concurrent connections, and none of our large customers have succeeded in running our VolanoChat product with JavaSoft's JVM on Windows NT. IBM's recent updates to its operating system, TCP/IP stack, and JVM have given it a huge 50 percent performance improvement over the VolanoMark 2.0 tests I ran without the updates (not shown here), but I could not get more than 400 concurrent connections with IBM's JVM.
We had been waiting for more than a year for a stable Solaris Java VM and Sun finally delivered.
The SunSoft JDK 1.1.5 VM for Solaris may be a bit laggard in its performance, but its reliability is rock solid. We had been waiting for more than a year for a stable Solaris Java virtual machine with native threads and a just-in-time compiler, and Sun finally delivered on April 6, 1998. For me this was the biggest Java news of this year, but it went completely unnoticed (perhaps because its robust performance was not immediately apparent to the trade press that covered its release). After working with Java virtual machines on the server since early 1996, I had begun to lower my expectations of quality -- but the SunSoft JDK 1.1.5 sets a new standard for stability. No other JVM comes close. We ran our VolanoChat demonstration server on this JVM for more than 32 days non-stop -- that's roughly 40 messages per second, 24 hours per day for 32 days, without any down time and without even going over its initial 8-MB heap size! I think it would have run forever, but I had to bring it down in order to upgrade the VolanoChat server. (In fact, we haven't rebooted the Solaris 2.6 operating system since we first set it up on our Internet Web and chat server machine on November 5, 1997.)
|Number of connections|
|Java Virtual Machine||2||100||200||300||400||500||600||700||800||900|
|Microsoft SDK 2.02||1751||2525||2090||1767||1556||1365||1242||1126||1030||946|
|JavaSoft JDK 1.1.6||1420||2082||1997||1797||1578||1381||1235||1099||1011||951|
|IBM JDK 1.1.6||1235||2009||1843||1853||1603||---||---||---||---||---|
|SunSoft JDK 1.1.5||902||1221||1134||1051||888||725||322||178||145||102|
|Apple MRJ 2.0||119||1090||950||781||877||767||---||---||---||---|
|Linux JDK 1.1.6||836||688||429||---||---||---||---||---||---||---|
|FreeBSD JDK 1.1.5||516||443||382||---||---||---||---||---||---||---|
Apple's Java virtual machine performed better than I had expected, although I had to restart the server between each test. The Linux and FreeBSD virtual machines do quite well considering that neither of them have a just-in-time compiler or native threads. For both Linux and FreeBSD, I was unable to get 300 concurrent connections or more, even after I increased their per-process file descriptor limits to more than 1000. In addition, the Linux and FreeBSD VMs have problems with the new Java 1.1 socket timeout feature, although I have been unable to isolate the cause. With the socket timeout feature enabled in the VolanoMark test, the Linux JVM runs extremely slowly and the FreeBSD JVM crashes with a core dump. Disabling the feature allowed them both to run the tests successfully.