[rules-users] Starting engine using fireUntilHalt and inserting no facts results in 50% CPU usage

[Greg Barton]

The problem is the race condition fix introduced in rev 30163.  The missedNotifyAll flag is set to true immediately which causes the busy loop.  
missedNotifyAll is initialized to false, but is immediately set to true because notifyHalt() is called in AbstractWorkingMemory.queueWorkingMemoryAction() via ReteooRuleBase.newStatefulSession().  Anyway, I'll move discussions of possible solutions over to the dev list, (crossposting now) or a JIRA if you'd prefer that.

--- On Mon, 10/25/10, Greg Barton <greg_barton at yahoo.com> wrote:

> From: Greg Barton <greg_barton at yahoo.com>
> Subject: Re: [rules-users] Starting engine using fireUntilHalt and inserting no facts results in 50% CPU usage
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Date: Monday, October 25, 2010, 3:18 PM
> I was going to look at this at some
> point.  I guess that point will be tonight. :)
> 
> GreG
> 
> On Oct 25, 2010, at 15:02, Edson Tirelli <tirelli at post.com>
> wrote:
> 
>   No worries, it is a good starting point anyway.
> Hopefully someone
> can continue from there or I will eventually fix it. Just a
> lot of
> stuff in my plate already that have priority over this.
> 
>   Edson
> 
> 2010/10/25 mardo <mardo at abicola.de>:
> Unfortunately no, I just had a look how it was implemented
> (like
> http://tutorials.jenkov.com/java-concurrency/thread-signaling.html#missedsig
> nals) -> missed signals and noticed that it somehow
> didn't work as intended.
> 
> But no idea how to directly correct it, sorry.
> 
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org]
> On Behalf Of Edson Tirelli
> Sent: Montag, 25. Oktober 2010 21:30
> To: Rules Users List
> Subject: Re: [rules-users] Starting engine using
> fireUntilHalt and inserting
> no facts results in 50% CPU usage
> 
>   Do you have a solution/patch for it?
> 
>   Edson
> 
> 2010/10/25 mardo <mardo at abicola.de>:
> Luckily just stumbled upon this mail...
> 
> You can take a look at
> 
> http://drools-java-rules-engine.46999.n3.nabble.com/fireUntilHalt-and-OSGi-C
> PU-load-td1022352.html
> 
> where I already provided a minimal example (don't know if
> it covers all
> cases) and tracked it down to missedNotifyAll in
> DefaultAgenda
> 
> cheers
> 
> 
> 
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org
> [mailto:rules-users-bounces at lists.jboss.org]
> On Behalf Of Edson Tirelli
> Sent: Montag, 25. Oktober 2010 21:17
> To: Rules Users List
> Subject: Re: [rules-users] Starting engine using
> fireUntilHalt and
> inserting
> no facts results in 50% CPU usage
> 
>  This is clearly a regression as Drools should be not be
> using busy
> waits in fireUntilHalt(). It should use monitors and locks
> as it was
> doing before.
> 
>  Can anyone open a JIRA? also, if anyone would be willing
> to take
> investigate and fix this one, it would really help.
> Otherwise, I will
> add it to my queue.
> 
>  Thanks,
> 
>   Edson
> 
> 2010/10/25 Norman C <rent_my_time at yahoo.com>:
> 
> 
> Note that the 100% CPU issue with fireUntiHalt is only with
> the 5.1
> version of
> Drools.  In 5.0.x, CPU is close to 0% when there are
> no rules to fire.  I
> saw
> this when I was testing upgrading to 5.1.
> 
> Norman
> 
> 
> 
> ----- Original Message ----
> From: jschmied <nabble at juergenschmied.de>
> To: rules-users at lists.jboss.org
> Sent: Sun, October 24, 2010 4:06:02 AM
> Subject: Re: [rules-users] Starting engine using
> fireUntilHalt and
> inserting no
> facts results in 50% CPU usage
> 
> 
> Hi!
> 
> fireUntilHalt uses one processor with 100%. You have a
> dualcore, so it's
> 50%. It's by design like this.
> 
> You can:
> - Call fireAllRules after every insert if you have no
> ruleflow.
> 
> - Use fireAllRules in a loop with a small sleep and check
> for the end of
> the
> ruleflow in the loop:
> 
> while (prc.getState() == ProcessInstance.STATE_ACTIVE) {
>     Threads.sleep(20);
>     ksession.fireAllRules();
> }
> 
> with both methods you get a low cpu load.
> 
> bye
> 
> juergen
> --
> View this message in context:
> 
> 
> http://drools-java-rules-engine.46999.n3.nabble.com/Starting-engine-using-fi
> 
> reUntilHalt-and-inserting-no-facts-results-in-50-CPU-usage-tp1760370p1761821
> .html
> 
> Sent from the Drools - User mailing list archive at
> Nabble.com.
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> 
> --
>   Edson Tirelli
>   JBoss Drools Core Development
>   JBoss by Red Hat @ www.jboss.com
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> --
>   Edson Tirelli
>   JBoss Drools Core Development
>   JBoss by Red Hat @ www.jboss.com
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> 
> -- 
>   Edson Tirelli
>   JBoss Drools Core Development
>   JBoss by Red Hat @ www.jboss.com
> 
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