I keep having issues with GC. Besides the cluster mentioned above, we also have a single node development cluster having the same issues. This node has 12.33 GB data, a couple of million skinny rows and basically no load. It has default memory settings but keep getting very long stop-the-world GC pauses: INFO [ScheduledTasks:1] 2013-06-07 10:37:02,537 GCInspector.java (line 122) GC for ParNew: 99342 ms for 1 collections, 1400754488 used; max is 4114612224 To try to rule out amount of memory, I set it to 16GB (we're on a virtual environment), with 4GB of it for Cassandra heap but that didn't help either, the incredibly long GC pauses keep coming. So I think something else is causing these issues, unless everyone is having really long GC pauses (which I doubt). I came across this thread: http://www.mail-archive.com/user@cassandra.apache.org/msg24042.html suggesting # date -s “`date`” might help my issues. It didn't however (unless I am supposed to replace that second date with the actual date?).
Has anyone had similar issues? 2013/4/17 aaron morton <aa...@thelastpickle.com> > > INFO [ScheduledTasks:1] 2013-04-15 14:00:02,749 GCInspector.java (line > 122) GC for ParNew: 338798 ms for 1 collections, 592212416 used; max is > 1046937600 > This does not say that the heap is full. > ParNew is GC activity for the new heap, which is typically a smaller part > of the overall heap. > > It sounds like you are running with defaults for the memory config, which > is generally a good idea. But 4GB total memory for a node is on the small > size. > > Try some changes, edit the cassandra-env.sh file and change > > MAX_HEAP_SIZE="2G" > HEAP_NEWSIZE="400M" > > You may also want to try: > > MAX_HEAP_SIZE="2G" > HEAP_NEWSIZE="800M" > JVM_OPTS="$JVM_OPTS -XX:SurvivorRatio=4" > JVM_OPTS="$JVM_OPTS -XX:MaxTenuringThreshold=2" > > The size of the new heap generally depends on the number of cores > available, see the commends in the -env file. > > An older discussion about memory use, not that in 1.2 the bloom filters > (and compression data) are off heap now. > http://www.mail-archive.com/user@cassandra.apache.org/msg25762.html > > Hope that helps. > > ----------------- > Aaron Morton > Freelance Cassandra Consultant > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 17/04/2013, at 11:06 PM, Joel Samuelsson <samuelsson.j...@gmail.com> > wrote: > > > You're right, it's probably hard. I should have provided more data. > > > > I'm running Ubuntu 10.04 LTS with JNA installed. I believe this line in > the log indicates that JNA is working, please correct me if I'm wrong: > > CLibrary.java (line 111) JNA mlockall successful > > > > Total amount of RAM is 4GB. > > > > My description of data size was very bad. Sorry about that. Data set > size is 12.3 GB per node, compressed. > > > > Heap size is 998.44MB according to nodetool info. > > Key cache is 49MB bytes according to nodetool info. > > Row cache size is 0 bytes acoording to nodetool info. > > Max new heap is 205MB kbytes according to Memory Pool "Par Eden Space" > max in jconsole. > > Memtable is left at default which should give it 333MB according to > documentation (uncertain where I can verify this). > > > > Our production cluster seems similar to your dev cluster so possibly > increasing the heap to 2GB might help our issues. > > > > I am still interested in getting rough estimates of how much heap will > be needed as data grows. Other than empirical studies how would I go about > getting such estimates? > > > > > > 2013/4/16 Viktor Jevdokimov <viktor.jevdoki...@adform.com> > > How one could provide any help without any knowledge about your cluster, > node and environment settings? > > > > > > > > 40GB was calculated from 2 nodes with RF=2 (each has 100% data range), > 2.4-2.5M rows * 6 cols * 3kB as a minimum without compression and any > overhead (sstable, bloom filters and indexes). > > > > > > > > With ParNew GC time such as yours even if it is a swapping issue I could > say only that heap size is too small. > > > > > > > > Check Heap, New Heap sizes, memtable and cache sizes. Are you on Linux? > Is JNA installed and used? What is total amount of RAM? > > > > > > > > Just for a DEV environment we use 3 virtual machines with 4GB RAM and > use 2GB heap without any GC issue with amount of data from 0 to 16GB > compressed on each node. Memtable space sized to 100MB, New Heap 400MB. > > > > > > > > Best regards / Pagarbiai > > Viktor Jevdokimov > > Senior Developer > > > > Email: viktor.jevdoki...@adform.com > > Phone: +370 5 212 3063, Fax +370 5 261 0453 > > J. Jasinskio 16C, LT-01112 Vilnius, Lithuania > > Follow us on Twitter: @adforminsider > > Take a ride with Adform's Rich Media Suite > > <signature-logo29.png> > > <signature-best-employer-logo4823.png> > > > > Disclaimer: The information contained in this message and attachments is > intended solely for the attention and use of the named addressee and may be > confidential. If you are not the intended recipient, you are reminded that > the information remains the property of the sender. You must not use, > disclose, distribute, copy, print or rely on this e-mail. If you have > received this message in error, please contact the sender immediately and > irrevocably delete this message and any copies. > > > > From: Joel Samuelsson [mailto:samuelsson.j...@gmail.com] > > Sent: Tuesday, April 16, 2013 12:52 > > To: user@cassandra.apache.org > > Subject: Re: Reduce Cassandra GC > > > > > > > > How do you calculate the heap / data size ratio? Is this a linear ratio? > > > > > > > > Each node has slightly more than 12 GB right now though. > > > > > > > > 2013/4/16 Viktor Jevdokimov <viktor.jevdoki...@adform.com> > > > > For a >40GB of data 1GB of heap is too low. > > > > > > > > Best regards / Pagarbiai > > > > Viktor Jevdokimov > > > > Senior Developer > > > > > > > > Email: viktor.jevdoki...@adform.com > > > > Phone: +370 5 212 3063, Fax +370 5 261 0453 > > > > J. Jasinskio 16C, LT-01112 Vilnius, Lithuania > > > > Follow us on Twitter: @adforminsider > > > > Take a ride with Adform's Rich Media Suite > > > > <image001.png> > > > > <image002.png> > > > > > > Disclaimer: The information contained in this message and attachments is > intended solely for the attention and use of the named addressee and may be > confidential. If you are not the intended recipient, you are reminded that > the information remains the property of the sender. You must not use, > disclose, distribute, copy, print or rely on this e-mail. If you have > received this message in error, please contact the sender immediately and > irrevocably delete this message and any copies. > > > > > > > > From: Joel Samuelsson [mailto:samuelsson.j...@gmail.com] > > Sent: Tuesday, April 16, 2013 10:47 > > To: user@cassandra.apache.org > > Subject: Reduce Cassandra GC > > > > > > > > Hi, > > > > > > > > We have a small production cluster with two nodes. The load on the nodes > is very small, around 20 reads / sec and about the same for writes. There > are around 2.5 million keys in the cluster and a RF of 2. > > > > > > > > About 2.4 million of the rows are skinny (6 columns) and around 3kb in > size (each). Currently, scripts are running, accessing all of the keys in > timeorder to do some calculations. > > > > > > > > While running the scripts, the nodes go down and then come back up 6-7 > minutes later. This seems to be due to GC. I get lines like this in the log: > > > > INFO [ScheduledTasks:1] 2013-04-15 14:00:02,749 GCInspector.java (line > 122) GC for ParNew: 338798 ms for 1 collections, 592212416 used; max is > 1046937600 > > > > > > > > However, the heap is not full. The heap usage has a jagged pattern going > from 60% up to 70% during 5 minutes and then back down to 60% the next 5 > minutes and so on. I get no "Heap is X full..." messages. Every once in a > while at one of these peaks, I get these stop-the-world GC for 6-7 minutes. > Why does GC take up so much time even though the heap isn't full? > > > > > > > > I am aware that my access patterns make key caching very unlikely to be > high. And indeed, my average key cache hit ratio during the run of the > scripts is around 0.5%. I tried disabling key caching on the accessed > column family (UPDATE COLUMN FAMILY cf WITH caching=none;) through the > cassandra-cli but I get the same behaviour. Is the turning key cache off > effective immediately? > > > > > > > > Stop-the-world GC is fine if it happens for a few seconds but having > them for several minutes doesn't work. Any other suggestions to remove them? > > > > > > > > Best regards, > > > > Joel Samuelsson > > > > > > > > > >
