Jenkins starts subprocesses which are not handled correctly, as some file handles are left open.

in htop you can see in the tree view that there are subprocess running even if no job is running and no scm polling is active.
these subprocesses consume memory and do not terminate by themselves

after picking the processID and getting the start time of the process, i could see, that the open file handle stated by the plugin 'Open File Handles' belonged to the scm polling.

ps -f 16734
UID PID PPID C STIME TTY STAT TIME CMD
tester 16734 399 0 16:55 ? S 0:00 /usr/lib64/jvm/java/bin/java -Djava.io.tmpdir=/archive/jenkins/tmp -Djava.awt.headless=true -Dhudson.model.Run.ArtifactList.listCutoff=40 -DJENKINS_HOME=/var/lib/jenkins -jar /usr/lib/jenkins/jenkins.war --javaHome=/usr/

output Open File Handles:
2 descriptors are open
#1 /var/lib/jenkins/...
#2 /var/lib/jenkins/jobs/.../scm-polling.log by thread:SCM polling for hudson.matrix.MatrixProject@1e88579c[...] on Tue Jun 19 16:55:02 CEST 2012
at java.io.FileOutputStream.<init>(FileOutputStream.java:211)
at java.io.FileOutputStream.<init>(FileOutputStream.java:160)
at hudson.util.StreamTaskListener.<init>(StreamTaskListener.java:97)
at hudson.util.StreamTaskListener.<init>(StreamTaskListener.java:90)
at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java:414)
at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:449)
at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:118)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:679)