We have a couple of users using CCTray to monitor build statuses.  When I look at the Current Requests in the JavaMelody monitoring page, there are always around ten requests for /job/<jobname>/api/json that have taken 20+ seconds to complete.  When I check what their threads are doing they are all Blocked on hudson.model.Fingerprint.addFor() or hudson.model.Fingerprint.save(), with this stack trace:

hudson.model.Fingerprint.addFor(Fingerprint.java:1023)
com.cloudbees.plugins.credentials.CredentialsProvider.trackAll(CredentialsProvider.java:1458)
com.cloudbees.plugins.credentials.CredentialsProvider.track(CredentialsProvider.java:1422)
org.jenkinsci.plugins.p4.client.ConnectionHelper.findCredential(ConnectionHelper.java:796)
org.jenkinsci.plugins.p4.client.ConnectionHelper.<init>(ConnectionHelper.java:99)
org.jenkinsci.plugins.p4.changes.P4ChangeParser$ChangeLogHandler.<init>(P4ChangeParser.java:68)
org.jenkinsci.plugins.p4.changes.P4ChangeParser.parse(P4ChangeParser.java:46)
hudson.scm.ChangeLogParser.parse(ChangeLogParser.java:57)
hudson.model.AbstractBuild.calcChangeSet(AbstractBuild.java:910)
hudson.model.AbstractBuild.getChangeSet(AbstractBuild.java:878)
java.lang.invoke.LambdaForm$DMH/517380410.invokeVirtual_L_L(LambdaForm$DMH)
java.lang.invoke.LambdaForm$BMH/1780704865.reinvoke(LambdaForm$BMH)
java.lang.invoke.LambdaForm$MH/151735829.invoke_MT(LambdaForm$MH)
org.kohsuke.stapler.export.MethodProperty.getValue(MethodProperty.java:72)
org.kohsuke.stapler.export.Property.safeGetValue(Property.java:152)
org.kohsuke.stapler.export.Property.writeTo(Property.java:133)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:227)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:223)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:223)
org.kohsuke.stapler.export.Property.writeValue(Property.java:317)
org.kohsuke.stapler.export.Property.writeBuffered(Property.java:181)
org.kohsuke.stapler.export.Property.writeValue(Property.java:242)
org.kohsuke.stapler.export.Property.writeValue(Property.java:175)
org.kohsuke.stapler.export.Property.writeTo(Property.java:146)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:227)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:223)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:223)
org.kohsuke.stapler.export.Model.writeNestedObjectTo(Model.java:223)
org.kohsuke.stapler.export.Model.writeTo(Model.java:198)
org.kohsuke.stapler.ResponseImpl.writeOne(ResponseImpl.java:285)
org.kohsuke.stapler.ResponseImpl.serveExposedBean(ResponseImpl.java:276)
hudson.model.Api.doJson(Api.java:208)
java.lang.invoke.LambdaForm$DMH/1655414169.invokeVirtual_L3_V(LambdaForm$DMH)
java.lang.invoke.LambdaForm$BMH/1397900113.reinvoke(LambdaForm$BMH)
java.lang.invoke.LambdaForm$MH/2106756990.invoker(LambdaForm$MH)
java.lang.invoke.LambdaForm$MH/6365533.invokeExact_MT(LambdaForm$MH)
java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:117)
org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:129)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
org.kohsuke.stapler.MetaClass$3.doDispatch(MetaClass.java:209)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
org.kohsuke.stapler.MetaClass$5.doDispatch(MetaClass.java:248)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
org.kohsuke.stapler.Stapler.service(Stapler.java:238)
javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
com.cloudbees.jenkins.support.slowrequest.SlowRequestFilter.doFilter(SlowRequestFilter.java:37)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:230)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:202)
net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:85)
org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:112)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
jenkins.metrics.impl.MetricsFilter.doFilter(MetricsFilter.java:125)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:126)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:49)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:73)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
org.eclipse.jetty.server.Server.handle(Server.java:499)
org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
java.lang.Thread.run(Thread.java:745)

I think the problem is that the P4 plugin calls CredentialsProvider.track every time findCredential is called, which seems unnecessary.  Surely track only needs to be called when a change to which credential is used is made in a job configuration?