CSS resources can be served stressfully with the following script:

while true; do for x in 1 2 3 4 5 6 7 8 9 0; do curl -H "Accept-Encoding: gzip,deflate" -O http://vorlon.ice:8080/component-showcase/xmlhttp/css/xp/css-images/over-right-mid.gif -O http://vorlon.ice:8080/component-showcase/xmlhttp/css/xp/xp.css& done; sleep 1; done

When this is run against a multiprocessor machine (both mac and linux have been tested),
after a short period the CPU utilization will go to 100% and will not subside until the server is killed. A typical thread in this state is the following:

  [1] java.util.zip.Deflater.deflateBytes (native method)
  [2] java.util.zip.Deflater.deflate (Deflater.java:284)
  [3] java.util.zip.DeflaterOutputStream.deflate (DeflaterOutputStream.java:154)
  [4] java.util.zip.DeflaterOutputStream.write (DeflaterOutputStream.java:114)
  [5] java.util.zip.GZIPOutputStream.write (GZIPOutputStream.java:72)
  [6] com.icesoft.faces.webapp.http.common.standard.CompressingServer.copy (CompressingServer.java:72)
  [7] com.icesoft.faces.webapp.http.common.standard.CompressingServer.access$200 (CompressingServer.java:15)
  [8] com.icesoft.faces.webapp.http.common.standard.CompressingServer$CompressingResponse.writeBodyFrom (CompressingServer.java:65)
  [9] com.icesoft.faces.webapp.http.core.ServeCSSResource$1.respond (ServeCSSResource.java:32)
  [10] com.icesoft.faces.webapp.http.common.standard.CacheControlledServer$EnhancedRequest$1.respond (CacheControlledServer.java:70)
  [11] com.icesoft.faces.webapp.http.common.standard.CompressingServer$CompressingRequest$1.respond (CompressingServer.java:44)
  [12] com.icesoft.faces.webapp.http.servlet.ServletRequestResponse.respondWith (ServletRequestResponse.java:121)
  [13] com.icesoft.faces.webapp.http.common.standard.CompressingServer$CompressingRequest.respondWith (CompressingServer.java:42)
  [14] com.icesoft.faces.webapp.http.common.standard.CacheControlledServer$EnhancedRequest.respondWith (CacheControlledServer.java:63)
  [15] com.icesoft.faces.webapp.http.core.ServeCSSResource.service (ServeCSSResource.java:29)
  [16] com.icesoft.faces.webapp.http.common.standard.CacheControlledServer.service (CacheControlledServer.java:42)
  [17] com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer$Matcher.serviceOnMatch (PathDispatcherServer.java:50)
  [18] com.icesoft.faces.webapp.http.common.standard.PathDispatcherServer.service (PathDispatcherServer.java:19)
  [19] com.icesoft.faces.webapp.http.common.standard.CompressingServer.service (CompressingServer.java:26)
  [20] com.icesoft.faces.webapp.http.core.ResourceServer.service (ResourceServer.java:30)
  [21] com.icesoft.faces.webapp.http.servlet.BasicAdaptingServlet.service (BasicAdaptingServlet.java:16)
  [22] com.icesoft.faces.webapp.http.servlet.PathDispatcher$Matcher.serviceOnMatch (PathDispatcher.java:41)
  [23] com.icesoft.faces.webapp.http.servlet.PathDispatcher.service (PathDispatcher.java:18)
  [24] com.icesoft.faces.webapp.http.servlet.MainServlet.service (MainServlet.java:47)
  [25] javax.servlet.http.HttpServlet.service (HttpServlet.java:802)
  [26] org.apache.catalina.core.ApplicationFilterChain.internalDoFilter (ApplicationFilterChain.java:237)
  [27] org.apache.catalina.core.ApplicationFilterChain.doFilter (ApplicationFilterChain.java:157)
  [28] org.apache.catalina.core.StandardWrapperValve.invoke (StandardWrapperValve.java:214)
  [29] org.apache.catalina.core.StandardValveContext.invokeNext (StandardValveContext.java:104)
  [30] org.apache.catalina.core.StandardPipeline.invoke (StandardPipeline.java:520)
  [31] org.apache.catalina.core.StandardContextValve.invokeInternal (StandardContextValve.java:198)
  [32] org.apache.catalina.core.StandardContextValve.invoke (StandardContextValve.java:152)
  [33] org.apache.catalina.core.StandardValveContext.invokeNext (StandardValveContext.java:104)
  [34] org.apache.catalina.core.StandardPipeline.invoke (StandardPipeline.java:520)
  [35] org.apache.catalina.core.StandardHostValve.invoke (StandardHostValve.java:137)
  [36] org.apache.catalina.core.StandardValveContext.invokeNext (StandardValveContext.java:104)
  [37] org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.java:118)
  [38] org.apache.catalina.core.StandardValveContext.invokeNext (StandardValveContext.java:102)
  [39] org.apache.catalina.core.StandardPipeline.invoke (StandardPipeline.java:520)
  [40] org.apache.catalina.core.StandardEngineValve.invoke (StandardEngineValve.java:109)
  [41] org.apache.catalina.core.StandardValveContext.invokeNext (StandardValveContext.java:104)
  [42] org.apache.catalina.core.StandardPipeline.invoke (StandardPipeline.java:520)
  [43] org.apache.catalina.core.ContainerBase.invoke (ContainerBase.java:929)
  [44] org.apache.coyote.tomcat5.CoyoteAdapter.service (CoyoteAdapter.java:160)
  [45] org.apache.coyote.http11.Http11Processor.process (Http11Processor.java:799)
  [46] org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection (Http11Protocol.java:705)
  [47] org.apache.tomcat.util.net.TcpWorkerThread.runIt (PoolTcpEndpoint.java:577)
  [48] org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run (ThreadPool.java:683)
  [49] java.lang.Thread.run (Thread.java:613)

By instrumenting the CompressingServer, it has been verified that the CPU activity is occurring only in the java.util.zip package. This is likely a zip implementation bug (lack of thread safety, perhaps in a native library) so the fix may be either to disable gzip encoding or to apply our own locking to ensure single threaded access to the gzip library.