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https://issues.apache.org/jira/browse/CASSANDRA-8447?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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jonathan lacefield updated CASSANDRA-8447:
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Attachment: output.1.svg
output.2.svg
output.1.svg represents "unhealthy" node, with compaction
output.2.svg represents "healthy" node, no compaction
These flame graphs were created to compare healthy and unhealthy nodes. They
were created after clearing out all CL replays by stopping dse, starting dse,
flushing nodes, stopping dse, restarting dse, finally validated CL replay was
not occurring through system.log.
The flame graphs were created on the same test execution.
> Nodes stuck in CMS GC cycle with very little traffic when compaction is
> enabled
> -------------------------------------------------------------------------------
>
> Key: CASSANDRA-8447
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8447
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: Cluster size - 4 nodes
> Node size - 12 CPU (hyper threaded to 24 cores), 192 GB RAM, 2 Raid 0 arrays
> (Data - 10 disk, spinning 10k drives | CL 2 disk, spinning 10k drives)
> OS - RHEL 6.5
> jvm - oracle 1.7.0_71
> Cassandra version 2.0.11
> Reporter: jonathan lacefield
> Attachments: Node_with_compaction.png, Node_without_compaction.png,
> cassandra.yaml, gc.logs.tar.gz, gcinspector_messages.txt, memtable_debug,
> output.1.svg, output.2.svg, output.svg, results.tar.gz, visualvm_screenshot
>
>
> Behavior - If autocompaction is enabled, nodes will become unresponsive due
> to a full Old Gen heap which is not cleared during CMS GC.
> Test methodology - disabled autocompaction on 3 nodes, left autocompaction
> enabled on 1 node. Executed different Cassandra stress loads, using write
> only operations. Monitored visualvm and jconsole for heap pressure.
> Captured iostat and dstat for most tests. Captured heap dump from 50 thread
> load. Hints were disabled for testing on all nodes to alleviate GC noise due
> to hints backing up.
> Data load test through Cassandra stress - /usr/bin/cassandra-stress write
> n=1900000000 -rate threads=<different threads tested> -schema
> replication\(factor=3\) keyspace="Keyspace1" -node <all nodes listed>
> Data load thread count and results:
> * 1 thread - Still running but looks like the node can sustain this load
> (approx 500 writes per second per node)
> * 5 threads - Nodes become unresponsive due to full Old Gen Heap. CMS
> measured in the 60 second range (approx 2k writes per second per node)
> * 10 threads - Nodes become unresponsive due to full Old Gen Heap. CMS
> measured in the 60 second range
> * 50 threads - Nodes become unresponsive due to full Old Gen Heap. CMS
> measured in the 60 second range (approx 10k writes per second per node)
> * 100 threads - Nodes become unresponsive due to full Old Gen Heap. CMS
> measured in the 60 second range (approx 20k writes per second per node)
> * 200 threads - Nodes become unresponsive due to full Old Gen Heap. CMS
> measured in the 60 second range (approx 25k writes per second per node)
> Note - the observed behavior was the same for all tests except for the single
> threaded test. The single threaded test does not appear to show this
> behavior.
> Tested different GC and Linux OS settings with a focus on the 50 and 200
> thread loads.
> JVM settings tested:
> # default, out of the box, env-sh settings
> # 10 G Max | 1 G New - default env-sh settings
> # 10 G Max | 1 G New - default env-sh settings
> #* JVM_OPTS="$JVM_OPTS -XX:CMSInitiatingOccupancyFraction=50"
> # 20 G Max | 10 G New
> JVM_OPTS="$JVM_OPTS -XX:+UseParNewGC"
> JVM_OPTS="$JVM_OPTS -XX:+UseConcMarkSweepGC"
> JVM_OPTS="$JVM_OPTS -XX:+CMSParallelRemarkEnabled"
> JVM_OPTS="$JVM_OPTS -XX:SurvivorRatio=8"
> JVM_OPTS="$JVM_OPTS -XX:MaxTenuringThreshold=8"
> JVM_OPTS="$JVM_OPTS -XX:CMSInitiatingOccupancyFraction=75"
> JVM_OPTS="$JVM_OPTS -XX:+UseCMSInitiatingOccupancyOnly"
> JVM_OPTS="$JVM_OPTS -XX:+UseTLAB"
> JVM_OPTS="$JVM_OPTS -XX:+CMSScavengeBeforeRemark"
> JVM_OPTS="$JVM_OPTS -XX:CMSMaxAbortablePrecleanTime=60000"
> JVM_OPTS="$JVM_OPTS -XX:CMSWaitDuration=30000"
> JVM_OPTS="$JVM_OPTS -XX:ParallelGCThreads=12"
> JVM_OPTS="$JVM_OPTS -XX:ConcGCThreads=12"
> JVM_OPTS="$JVM_OPTS -XX:+UnlockDiagnosticVMOptions"
> JVM_OPTS="$JVM_OPTS -XX:+UseGCTaskAffinity"
> JVM_OPTS="$JVM_OPTS -XX:+BindGCTaskThreadsToCPUs"
> JVM_OPTS="$JVM_OPTS -XX:ParGCCardsPerStrideChunk=32768"
> JVM_OPTS="$JVM_OPTS -XX:-UseBiasedLocking"
> # 20 G Max | 1 G New
> JVM_OPTS="$JVM_OPTS -XX:+UseParNewGC"
> JVM_OPTS="$JVM_OPTS -XX:+UseConcMarkSweepGC"
> JVM_OPTS="$JVM_OPTS -XX:+CMSParallelRemarkEnabled"
> JVM_OPTS="$JVM_OPTS -XX:SurvivorRatio=8"
> JVM_OPTS="$JVM_OPTS -XX:MaxTenuringThreshold=8"
> JVM_OPTS="$JVM_OPTS -XX:CMSInitiatingOccupancyFraction=75"
> JVM_OPTS="$JVM_OPTS -XX:+UseCMSInitiatingOccupancyOnly"
> JVM_OPTS="$JVM_OPTS -XX:+UseTLAB"
> JVM_OPTS="$JVM_OPTS -XX:+CMSScavengeBeforeRemark"
> JVM_OPTS="$JVM_OPTS -XX:CMSMaxAbortablePrecleanTime=60000"
> JVM_OPTS="$JVM_OPTS -XX:CMSWaitDuration=30000"
> JVM_OPTS="$JVM_OPTS -XX:ParallelGCThreads=12"
> JVM_OPTS="$JVM_OPTS -XX:ConcGCThreads=12"
> JVM_OPTS="$JVM_OPTS -XX:+UnlockDiagnosticVMOptions"
> JVM_OPTS="$JVM_OPTS -XX:+UseGCTaskAffinity"
> JVM_OPTS="$JVM_OPTS -XX:+BindGCTaskThreadsToCPUs"
> JVM_OPTS="$JVM_OPTS -XX:ParGCCardsPerStrideChunk=32768"
> JVM_OPTS="$JVM_OPTS -XX:-UseBiasedLocking"
> Linux OS settings tested:
> # Disabled Transparent Huge Pages
> echo never > /sys/kernel/mm/transparent_hugepage/enabled
> echo never > /sys/kernel/mm/transparent_hugepage/defrag
> # Enabled Huge Pages
> echo 21500000000 > /proc/sys/kernel/shmmax (over 20GB for heap)
> echo 1536 > /proc/sys/vm/nr_hugepages (20GB/2MB page size)
> # Disabled NUMA
> numa-off in /etc/grub.confdatastax
> # Verified all settings documented here were implemented
>
> http://www.datastax.com/documentation/cassandra/2.0/cassandra/install/installRecommendSettings.html
> Attachments:
> # .yaml
> # fio output - results.tar.gz
> # 50 thread heap dump -
> https://drive.google.com/a/datastax.com/file/d/0B4Imdpu2YrEbMGpCZW5ta2liQ2c/view?usp=sharing
> # 100 thread - visual vm anonymous screenshot - visualvm_screenshot
> # dstat screen shot of with compaction - Node_with_compaction.png
> # dstat screen shot of without compaction -- Node_without_compaction.png
> # gcinspector messages from system.log
> # gc.log output - gc.logs.tar.gz
> Observations:
> # even though this is a spinning disk implementation, disk io looks good.
> #* output from Jshook perf monitor https://github.com/jshook/perfscripts is
> attached
> #* note, we leveraged direct io for all tests by adding direct=1 to the
> .global config files
> # cpu usage is moderate until large GC events occur
> # once old gen heap fills up and cannot clean, memtable post flushers start
> to back up (show a lot pending) via tpstats
> # the node itself, i.e. ssh, is still responsive but the Cassandra instance
> becomes unresponsive
> # once old gen heap fills up Cassandra stress starts to throw CL ONE errors
> stating there aren't enough replicas to satisfy....
> # heap dump from 50 thread, JVM scenario 1 is attached
> #* appears to show a compaction thread consuming a lot of memory
> # sample system.log output for gc issues
> # strace -e futex -p $PID -f -c output during 100 thread load and during old
> gen "filling", just before full
> % time seconds usecs/call calls errors syscall
> 100.00 244.886766 4992 49052 7507 futex
> 100.00 244.886766 49052 7507 total
> # htop during full gc cycle -
> https://s3.amazonaws.com/uploads.hipchat.com/6528/480117/4ZlgcoNScb6kRM2/upload.png
> # nothing is blocked via tpstats on these nodes
> # compaction does have pending tasks, upwards of 20, on the nodes
> # Nodes without compaction achieved approximately 20k writes per second per
> node without errors or drops
> Next Steps:
> # Will try to create a flame graph and update load here -
> http://www.brendangregg.com/blog/2014-06-12/java-flame-graphs.html
> # Will try to recreate in another environment
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