Could you try 8.1.1?
It's had some significant updates with regards to nio.

http://repo1.maven.org/maven2/org/eclipse/jetty/jetty-distribution/8.1.1.v20120215/

Usually something like the behavior you describe would trigger me asking
about your GC setup, but I can see that's configured / tweaked quite well.

--
Joakim Erdfelt
[email protected]

http://webtide.com | http://intalio.com
(the people behind jetty and cometd)



On Wed, Feb 29, 2012 at 2:17 PM, Vinay Pothnis <[email protected]>wrote:

> Hello,
>
> I am seeing a periodic CPU spike when the Jetty server is handling
> requests. The spike occurs regularly every *5 minutes* and uses up
> 90-100% CPU for a short duration.
> The CPU utilization falls back to normal after that short spike. This
> happens only when the server is receiving requests.
>
> I have taken thread dumps during several spikes and I have not been able
> to conclude anything concrete. In the dumps I observed the following:
>
> 1. There were hundreds of threads in BLOCKED state waiting for a lock held
> by a thread.
> 2. The thread that was holding the lock was in turn BLOCKED. But it was
> not waiting for any other lock. Example shown below.
>
> "qtp732533575-307956" prio=10 tid=0x00002aad980c4800 nid=0x3e1f waiting for 
> monitor entry [0x0000000067f69000]
>    java.lang.Thread.State: BLOCKED (on object monitor)
>       at org.hibernate.util.SoftLimitMRUCache.get(SoftLimitMRUCache.java:74)
>       - locked <0x00002aabefafa198> (a org.hibernate.util.SoftLimitMRUCache)
>       at 
> org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:88)
>       at 
> org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156)
>       at 
> org.hibernate.impl.AbstractSessionImpl.getNamedQuery(AbstractSessionImpl.java:82)
>       at org.hibernate.impl.SessionImpl.getNamedQuery(SessionImpl.java:1287)  
> at sun.reflect.GeneratedMethodAccessor202.invoke(Unknown Source)
>
> 3. The actual lock that the threads were waiting on, varied. It was not
> the same in the different spikes every 5 minutes.
>
> *Environment Details:*
> * Embedded Jetty Version 8.0.4
> * Java 1.6.0_17
> * Red Hat Enterprise Linux Server release 5.2 (Tikanga)
>
> *JVM Parameters:*
> -server -Xmx11g -Xms11g -XX:MaxPermSize=256m -XX:+UseParNewGC
> -XX:+UseConcMarkSweepGC -XX:NewSize=5g -XX:MaxNewSize=5g
> -XX:SurvivorRatio=6 -XX:+PrintGCDetails
> -XX:+PrintGCTimeStamps -Dsun.rmi.dgc.client.gcInterval=3600000
> -Dsun.rmi.dgc.server.gcInterval=3600000
>
> I have also attached the CPU usage pattern. Any pointers would be greatly
> appreciated.
>
> Thanks!
> Vinay
>
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>
>
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