Virtualization
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650MB of virtual space is a lot. If you moreover realize that [[hudson]] starts multiple [[Java]] [[VM]]s in parallel, it is easy to see that the system can't work. Indeed it did not: swap was full all the time, sometimes the [[VirtualBox]] machine rebooted, etc. | 650MB of virtual space is a lot. If you moreover realize that [[hudson]] starts multiple [[Java]] [[VM]]s in parallel, it is easy to see that the system can't work. Indeed it did not: swap was full all the time, sometimes the [[VirtualBox]] machine rebooted, etc. | ||
| - | For a while I was searching for a solution. I tried to pass in '''-mx64M''' into every started process, but as far as I can tell, this is not easy. There does not seem to be any configuration file the ''java'' launcher reads (''jvm.cfg'' is not the one, one cannot specify there default command line arguments). | + | For a while I was searching for a solution. I tried to pass in '''-mx64M''' into every started process, but as far as I can tell, this is not easy. There does not seem to be any configuration file the ''java'' launcher reads (''jvm.cfg'' is not the one, one cannot specify there default command line arguments). |
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| + | One can specify the parameter on command line, which is not practical. If you don't start the process yourself, how do you influence command line? That is why I renamed ''java'' to ''java.openjdk'' and replaced ''java'' with a shell script to call the ''java.openjdk'' with proper parameter. This worked, but only for ''java'', not for ''javadoc'', etc. So I was not satisfied with the solution at all. | ||
Then a friend of mine suggested to try official [[JDK]], not just [[OpenJDK]] variant. I hesitated for a while, but then I decided to try it. Here is the ''top'' output: | Then a friend of mine suggested to try official [[JDK]], not just [[OpenJDK]] variant. I hesitated for a while, but then I decided to try it. Here is the ''top'' output: | ||
Revision as of 14:17, 14 June 2010
Virtualization is an important aspect in cluelessness. Instead of improving own application, or making it more secure, one can run it in an isolated, dedicated virtual computer. It may require more memory or more powerful processors, but the need of software quality is lower and thus one can achive more by knowing less - the credo of cluelessness.
OpenJDK
I wanted to run this site's associated hudson builder in an isolated environment. Originally I was using vserver, but after my hard disk crashed, I decided to try VirtualBox.
I am running Kubuntu as host and also a stripped down version of Kubuntu as a guest. I have given the guest 384MB of memory and 400MB of swap. To my biggest surprise, running even smallest Java program on OpenJDK in such environment allocated 650MB(!!!) of virtual addressing space. Just check the top output:
Tasks: 81 total, 1 running, 80 sleeping, 0 stopped, 0 zombie Cpu(s): 0.7%us, 4.7%sy, 0.0%ni, 94.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 379872k total, 306828k used, 73044k free, 40164k buffers Swap: 407544k total, 16064k used, 391480k free, 111272k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4129 hudson 20 0 655m 10m 7484 S 2.3 2.8 0:01.02 java.openjdk 4210 hudson 20 0 5248 3500 1556 S 0.0 0.9 0:00.87 bash 4144 root 20 0 8856 3048 2412 S 0.0 0.8 0:00.40 sshd 1619 postfix 20 0 6244 2544 1812 S 0.0 0.7 0:00.12 tlsmgr 951 hudson 20 0 5248 2008 1280 S 0.0 0.5 0:01.08 bash
650MB of virtual space is a lot. If you moreover realize that hudson starts multiple Java VMs in parallel, it is easy to see that the system can't work. Indeed it did not: swap was full all the time, sometimes the VirtualBox machine rebooted, etc.
For a while I was searching for a solution. I tried to pass in -mx64M into every started process, but as far as I can tell, this is not easy. There does not seem to be any configuration file the java launcher reads (jvm.cfg is not the one, one cannot specify there default command line arguments).
One can specify the parameter on command line, which is not practical. If you don't start the process yourself, how do you influence command line? That is why I renamed java to java.openjdk and replaced java with a shell script to call the java.openjdk with proper parameter. This worked, but only for java, not for javadoc, etc. So I was not satisfied with the solution at all.
Then a friend of mine suggested to try official JDK, not just OpenJDK variant. I hesitated for a while, but then I decided to try it. Here is the top output:
Tasks: 81 total, 2 running, 79 sleeping, 0 stopped, 0 zombie Cpu(s): 1.0%us, 2.3%sy, 0.0%ni, 96.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 379872k total, 307924k used, 71948k free, 40388k buffers Swap: 407544k total, 16056k used, 391488k free, 111424k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4306 hudson 20 0 239m 10m 6956 S 0.0 2.8 0:00.48 java 4210 hudson 20 0 5248 3500 1556 S 0.0 0.9 0:00.88 bash 4144 root 20 0 8856 3048 2412 S 0.0 0.8 0:00.40 sshd
Better. The 240M of occupried space is still much more than I'd like to see (no wonder nobody offers free hosting of Java applications), but at least it fits into real memory. By using JDK 1.6.0_20 I can really run my Hudson in VirtualBox with 384M of memory.
Conclusion? OpenJDK seems to contain a bug in a launcher which makes it completely unsuitable for running in a virtualized environment!
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