How much memory your jvm is taking? Do you even have enough disk space to dump it. From: Abdel Hakim Deneche <adene...@maprtech.com> To: "dev@drill.apache.org" <dev@drill.apache.org> Sent: Friday, July 31, 2015 9:19 PM Subject: Re: Suspicious direct memory consumption when running queries concurrently I tried getting a jmap dump multiple times without success, each time it crashes the jvm with the following exception:
Dumping heap to /home/mapr/private-sql-hadoop-test/framework/myfile.hprof > ... > Exception in thread "main" java.io.IOException: Premature EOF > at > sun.tools.attach.HotSpotVirtualMachine.readInt(HotSpotVirtualMachine.java:248) > at > sun.tools.attach.LinuxVirtualMachine.execute(LinuxVirtualMachine.java:199) > at > sun.tools.attach.HotSpotVirtualMachine.executeCommand(HotSpotVirtualMachine.java:217) > at > sun.tools.attach.HotSpotVirtualMachine.dumpHeap(HotSpotVirtualMachine.java:180) > at sun.tools.jmap.JMap.dump(JMap.java:242) > at sun.tools.jmap.JMap.main(JMap.java:140) On Mon, Jul 27, 2015 at 3:45 PM, Jacques Nadeau <jacq...@dremio.com> wrote: > A allocate -> release cycle all on the same thread goes into a per thread > cache. > > A bunch of Netty arena settings are configurable. The big issue I believe > is that the limits are soft limits implemented by the allocation-time > release mechanism. As such, if you allocate a bunch of memory, then > release it all, that won't necessarily trigger any actual chunk releases. > > -- > Jacques Nadeau > CTO and Co-Founder, Dremio > > On Mon, Jul 27, 2015 at 12:47 PM, Abdel Hakim Deneche < > adene...@maprtech.com > > wrote: > > > @Jacques, my understanding is that chunks are not owned by specific a > > thread but they are part of a specific memory arena which is in turn only > > accessed by specific threads. Do you want me to find which threads are > > associated with the same arena where we have hanging chunks ? > > > > > > On Mon, Jul 27, 2015 at 11:04 AM, Jacques Nadeau <jacq...@dremio.com> > > wrote: > > > > > It sounds like your statement is that we're cacheing too many unused > > > chunks. Hanifi and I previously discussed implementing a separate > > flushing > > > mechanism to release unallocated chunks that are hanging around. The > > main > > > question is, why are so many chunks hanging around and what threads are > > > they associated with. A Jmap dump and analysis should allow you to do > > > determine which thread owns the excess chunks. My guess would be the > RPC > > > pool since those are long lasting (as opposed to the WorkManager pool, > > > which is contracting). > > > > > > -- > > > Jacques Nadeau > > > CTO and Co-Founder, Dremio > > > > > > On Mon, Jul 27, 2015 at 9:53 AM, Abdel Hakim Deneche < > > > adene...@maprtech.com> > > > wrote: > > > > > > > When running a set of, mostly window function, queries concurrently > on > > a > > > > single drillbit with a 8GB max direct memory. We are seeing a > > continuous > > > > increase of direct memory allocation. > > > > > > > > We repeat the following steps multiple times: > > > > - we launch in "iteration" of tests that will run all queries in a > > random > > > > order, 10 queries at a time > > > > - after the iteration finishes, we wait for a couple of minute to > give > > > > Drill time to release the memory being held by the finishing > fragments > > > > > > > > Using Drill's memory logger ("drill.allocator") we were able to get > > > > snapshots of how memory was internally used by Netty, we only focused > > on > > > > the number of allocated chunks, if we take this number and multiply > it > > by > > > > 16MB (netty's chunk size) we get approximately the same value > reported > > by > > > > Drill's direct memory allocation. > > > > Here is a graph that shows the evolution of the number of allocated > > > chunks > > > > on a 500 iterations run (I'm working on improving the plots) : > > > > > > > > http://bit.ly/1JL6Kp3 > > > > > > > > In this specific case, after the first iteration Drill was allocating > > > ~2GB > > > > of direct memory, this number kept rising after each iteration to > ~6GB. > > > We > > > > suspect this caused one of our previous runs to crash the JVM. > > > > > > > > If we only focus on the log lines between iterations (when Drill's > > memory > > > > usage is below 10MB) then all allocated chunks are at most 2% usage. > At > > > > some point we end up with 288 nearly empty chunks, yet the next > > iteration > > > > will cause more chunks to be allocated!!! > > > > > > > > is this expected ? > > > > > > > > PS: I am running more tests and will update this thread with more > > > > informations. > > > > > > > > -- > > > > > > > > Abdelhakim Deneche > > > > > > > > Software Engineer > > > > > > > > <http://www.mapr.com/> > > > > > > > > > > > > Now Available - Free Hadoop On-Demand Training > > > > < > > > > > > > > > > http://www.mapr.com/training?utm_source=Email&utm_medium=Signature&utm_campaign=Free%20available > > > > > > > > > > > > > > > > > > > > -- > > > > Abdelhakim Deneche > > > > Software Engineer > > > > <http://www.mapr.com/> > > > > > > Now Available - Free Hadoop On-Demand Training > > < > > > http://www.mapr.com/training?utm_source=Email&utm_medium=Signature&utm_campaign=Free%20available > > > > > > -- Abdelhakim Deneche Software Engineer <http://www.mapr.com/> Now Available - Free Hadoop On-Demand Training <http://www.mapr.com/training?utm_source=Email&utm_medium=Signature&utm_campaign=Free%20available>