Was running 1.506 jenkins, and then rolled forward to 1.527. (also updated plugins, which I won't list here unless we think there is a specific one that might be causing the problem).

Didn't change any jobs, just kept running as-is.

Suddenly, after the server has been up for more than a couple days I start getting these messages:
FATAL: PermGen space
java.lang.OutOfMemoryError: PermGen space
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
at org.apache.tools.ant.AntClassLoader.defineClassFromData(AntClassLoader.java:1128)
at hudson.ClassicPluginStrategy$AntClassLoader2.defineClassFromData(ClassicPluginStrategy.java:696)
at org.apache.tools.ant.AntClassLoader.getClassFromStream(AntClassLoader.java:1299)
at org.apache.tools.ant.AntClassLoader.findClassInComponents(AntClassLoader.java:1355)
at org.apache.tools.ant.AntClassLoader.findClass(AntClassLoader.java:1315)
at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1068)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
at org.apache.http.impl.conn.PoolingClientConnectionManager.leaseConnection(PoolingClientConnectionManager.java:222)
at org.apache.http.impl.conn.PoolingClientConnectionManager$1.getConnection(PoolingClientConnectionManager.java:199)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:456)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:805)
at org.apache.maven.wagon.shared.http4.AbstractHttpClientWagon.execute(AbstractHttpClientWagon.java:746)
at org.apache.maven.wagon.shared.http4.AbstractHttpClientWagon.fillInputData(AbstractHttpClientWagon.java:886)
at org.apache.maven.wagon.StreamWagon.getInputStream(StreamWagon.java:116)
at org.apache.maven.wagon.StreamWagon.getIfNewer(StreamWagon.java:88)
at org.apache.maven.wagon.StreamWagon.get(StreamWagon.java:61)
at org.eclipse.aether.connector.wagon.WagonRepositoryConnector$GetTask.run(WagonRepositoryConnector.java:660)
at org.eclipse.aether.util.concurrency.RunnableErrorForwarder$1.run(RunnableErrorForwarder.java:67)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:679)

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Something has changed recently that is slowly using up more and more memory, because this wasn't an issue before. I've even tried increasing the amount of permgen space available and that has had no measurable effect.