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2 Replies Latest reply: Jun 14, 2010 3:55 AM by 807557 RSS

Too many RTGC threads running

807557 Newbie
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I am running my application with following settings

-Xloggc:gc.log -XX:+UseITC -XX:RTSJBindRTTToProcessorSet=1 -XX:RTGCNormalWorkers=2 -Xms1G -Xmx1G -XX:NormalMinFreeBytes=1G -XX:RTGCCriticalReservedBytes=256M

Processor set defined as above consists of 4 cpus. Total cpu on this box are 16. My application has a single RTT running a busy loop. I am assigning 2 threads for RTGC, but when I look at summary<pid>.txt generated by TSV, it shows 15 RTGC threads one named RTGC Thread#0 and all other are Gang worker#<i> (RTGC Threads). Should not only two RTGC threads should be running.

I have 4 cpus assigned for running real time threads and I expect maximum 3 real time threads at any point of time(1 application and two RTGC threads), I am keeping actual RTT count lower than cpus available to make sure that no RTT should hop cpus but tsv summary suggests that there are 1-5 hops happening in case of application real time thread. Application thread is running a loop which do exactly same calculations in each iteration and measure time taken by this calculation. When I plot calculation time i see few peaks which are around 120 micro seconds higher than median of 137 micro seconds. Also near these peaks there is some jitter in range of ~50 micros above median.

Could you please explain that?