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I have a simple 3 tier setup of an Apache server which sends requests to a Tomcat server, which queries a (MySQL) database to generate HTML results. I'm finding that as soon as Tomcat is started, there are threads in the java process that are spinning away making futex() calls. After a few dozens web requests, the threads trying to serve requests get caught in the same futex() loops, and it stops answering all requests -- they time out on the client side.

I have tried this in Tomcat 6 and Tomcat 7. I have tried it with Oracle's Java 1.7.0_45 and OpenJDK 1.6.0. This VM is a 64 bit Redhat 6 system, and I have tried with their released 2.6.32-358.23.2 kernel and their 2.6.32-431.3.1 kernel, and all combinations are showing these system calls in strace, and eventually locking up.

futex(an addr, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1, {a timestamp}, ffffffff)
 = -1 ETIMEDOUT (Connection timed out)
futex(an addr, FUTEX_WAKE_PRIVATE, 1) = 0

The JVM does this with the default memory, or even if I increase the available mem to 3GB (of the 4GB on the machine). I ran with a GC logger, and GC printed a few minor collections, and was not doing one when the lockup occurred. This machine was created in Jan 2014, so is not in any "leap second" situations.

So my questions would be: why is Java making all of these futex() calls in a fast loop even when the JVM should be "idle"? are they normal? should they be getting the timeout? and is there a known fix?

Thank you for info insights.

user3361382
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1 Answers1

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i have the same problem,i suspect its the "leap second" caused so. my java processes have a high cpu load for a long time.i get a file "leap-a-day.c" from http://marc.info/?t=134138331900001&r=1&w=2,and run as "./leap-a-day -s",and cpu load suddenly become low,i dont know why....my os is redhat as6.5

Oliver I
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user3929438
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