mirror of https://github.com/apache/cassandra
Heap and GC jvm flags improvements
G1 can rely on `-XX:G1NewSizePercent=50` to always floor the young generation's size to 50% of the heap. (In production this can be raised to 66% for optimal performance.) Fixing the young generation size with `-Xmn` is only applicable to CMS, so move it to the appropriate section. When using G1, we can automatically set `-XX:ParallelGCThreads` and `-XX:ConcGCThreads` to the number of system cpu cores. The auto-generated heap size is now half the server's physical RAM, capped at 16G for CMS and 31G for G1. Increase MaxTenuringThreshold from 1 to 2, as evidence has shown it has no cost (over values of zero or one), but can have significant benefits in keeping objects in the young generation. While, values above 2 don't have any noticeable benefit. Always set CASSANDRA_HEAPDUMP_DIR, default it to $CASSANDRA_LOG_DIR, to avoid hprof filling up unexpected disk volumes. Assumption here is that the logs directory is large enough to handle these dumps, and/or operators are monitoring these directories more than other randon/unknown directories. patch by Mick Semb Wever; reviewed by Jon Haddad for CASSANDRA-20296
This commit is contained in:
mck
parent
027689ae48
commit
0034a133fa
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@ -44,45 +44,24 @@ calculate_heap_sizes()
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esac
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# some systems like the raspberry pi don't report cores, use at least 1
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if [ "$system_cpu_cores" -lt "1" ]
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then
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if [ "$system_cpu_cores" -lt "1" ] ; then
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system_cpu_cores="1"
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fi
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# set max heap size based on the following
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# max(min(1/2 ram, 1024MB), min(1/4 ram, 8GB))
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# calculate 1/2 ram and cap to 1024MB
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# calculate 1/4 ram and cap to 8192MB
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# pick the max
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# Heap size: min(1/2 ram, CMS ? 16G : 31G)
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# CMS Young gen: 1/2 * heap size
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if [ $USING_CMS -eq 0 ] ; then
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heap_limit="15872"
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else
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heap_limit="31744"
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fi
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half_system_memory_in_mb=`expr $system_memory_in_mb / 2`
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quarter_system_memory_in_mb=`expr $half_system_memory_in_mb / 2`
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if [ "$half_system_memory_in_mb" -gt "1024" ]
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then
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half_system_memory_in_mb="1024"
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fi
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if [ "$quarter_system_memory_in_mb" -gt "8192" ]
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then
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quarter_system_memory_in_mb="8192"
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fi
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if [ "$half_system_memory_in_mb" -gt "$quarter_system_memory_in_mb" ]
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then
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max_heap_size_in_mb="$half_system_memory_in_mb"
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if [ "$half_system_memory_in_mb" -gt "$heap_limit" ] ; then
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CALCULATED_MAX_HEAP_SIZE="${heap_limit}M"
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CALCULATED_CMS_HEAP_NEWSIZE="8G"
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else
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max_heap_size_in_mb="$quarter_system_memory_in_mb"
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fi
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MAX_HEAP_SIZE="${max_heap_size_in_mb}M"
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# Young gen: min(max_sensible_per_modern_cpu_core * num_cores, 1/4 * heap size)
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max_sensible_yg_per_core_in_mb="100"
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max_sensible_yg_in_mb=`expr $max_sensible_yg_per_core_in_mb "*" $system_cpu_cores`
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desired_yg_in_mb=`expr $max_heap_size_in_mb / 4`
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if [ "$desired_yg_in_mb" -gt "$max_sensible_yg_in_mb" ]
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then
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HEAP_NEWSIZE="${max_sensible_yg_in_mb}M"
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else
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HEAP_NEWSIZE="${desired_yg_in_mb}M"
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CALCULATED_MAX_HEAP_SIZE="${half_system_memory_in_mb}M"
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CALCULATED_CMS_HEAP_NEWSIZE="`expr $half_system_memory_in_mb / 4`M"
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fi
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}
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@ -108,35 +87,44 @@ echo $JVM_OPTS | grep -q Xmx
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DEFINED_XMX=$?
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echo $JVM_OPTS | grep -q Xms
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DEFINED_XMS=$?
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echo $JVM_OPTS | grep -q ParallelGCThreads
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DEFINED_PARALLEL_GC_THREADS=$?
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echo $JVM_OPTS | grep -q ConcGCThreads
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DEFINED_CONC_GC_THREADS=$?
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echo $JVM_OPTS | grep -q UseConcMarkSweepGC
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USING_CMS=$?
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echo $JVM_OPTS | grep -q +UseG1GC
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USING_G1=$?
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calculate_heap_sizes
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# Override these to set the amount of memory to allocate to the JVM at
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# start-up. For production use you may wish to adjust this for your
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# environment. MAX_HEAP_SIZE is the total amount of memory dedicated
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# to the Java heap. HEAP_NEWSIZE refers to the size of the young
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# generation. Both MAX_HEAP_SIZE and HEAP_NEWSIZE should be either set
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# generation when CMS is used.
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#
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# When using G1 only MAX_HEAP_SIZE may be set, and HEAP_NEWSIZE must be
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# left unset.
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#
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# When using CMS both MAX_HEAP_SIZE and HEAP_NEWSIZE should be either set
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# or not (if you set one, set the other).
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#
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# The main trade-off for the young generation is that the larger it
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# is, the longer GC pause times will be. The shorter it is, the more
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# expensive GC will be (usually).
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#
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# The example HEAP_NEWSIZE assumes a modern 8-core+ machine for decent pause
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# times. If in doubt, and if you do not particularly want to tweak, go with
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# 100 MB per physical CPU core.
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#MAX_HEAP_SIZE="4G"
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#HEAP_NEWSIZE="800M"
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#MAX_HEAP_SIZE="20G"
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#HEAP_NEWSIZE="10G"
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# Set this to control the amount of arenas per-thread in glibc
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#export MALLOC_ARENA_MAX=4
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# only calculate the size if it's not set manually
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# Warn on an erroneously set HEAP_NEWSIZE when using G1
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if [ "x$HEAP_NEWSIZE" != "x" -a $USING_G1 -eq 0 ]; then
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echo "HEAP_NEWSIZE has erroneously been set and will be ignored in combination with G1 (see cassandra-env.sh)"
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fi
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# Only use the calculated size if it's not set manually
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if [ "x$MAX_HEAP_SIZE" = "x" ] && [ "x$HEAP_NEWSIZE" = "x" -o $USING_G1 -eq 0 ]; then
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calculate_heap_sizes
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MAX_HEAP_SIZE="$CALCULATED_MAX_HEAP_SIZE"
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HEAP_NEWSIZE="$CALCULATED_CMS_HEAP_NEWSIZE"
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elif [ "x$MAX_HEAP_SIZE" = "x" ] || [ "x$HEAP_NEWSIZE" = "x" -a $USING_G1 -ne 0 ]; then
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echo "please set or unset MAX_HEAP_SIZE and HEAP_NEWSIZE in pairs when using CMS GC (see cassandra-env.sh)"
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exit 1
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@ -157,8 +145,7 @@ elif [ $DEFINED_XMX -ne 0 ] || [ $DEFINED_XMS -ne 0 ]; then
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fi
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# We only set -Xmn flag if it was not defined in jvm-server.options file
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# and if the CMS GC is being used
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# If defined, both Xmn and Xmx should be defined together.
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# and CMS is being used. If defined, both Xmn and Xmx must be defined together.
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if [ $DEFINED_XMN -eq 0 ] && [ $DEFINED_XMX -ne 0 ]; then
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echo "Please set or unset -Xmx and -Xmn flags in pairs on jvm-server.options file."
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exit 1
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@ -166,13 +153,22 @@ elif [ $DEFINED_XMN -ne 0 ] && [ $USING_CMS -eq 0 ]; then
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JVM_OPTS="$JVM_OPTS -Xmn${HEAP_NEWSIZE}"
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fi
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# We fail to start if -Xmn is used with G1 GC is being used
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# See comments for -Xmn in jvm-server.options
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# We fail to start if -Xmn is used with G1
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if [ $DEFINED_XMN -eq 0 ] && [ $USING_G1 -eq 0 ]; then
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# It is not recommended to set the young generation size if using the
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# G1 GC, since that will override the target pause-time goal.
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# Instead floor the young generation size with -XX:NewSize
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# More info: http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html
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echo "It is not recommended to set -Xmn with the G1 garbage collector. See comments for -Xmn in jvm-server.options for details."
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exit 1
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fi
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if [ $USING_G1 -eq 0 ] && [ $DEFINED_PARALLEL_GC_THREADS -ne 0 ] && [ $DEFINED_CONC_GC_THREADS -ne 0 ] ; then
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# Set ParallelGCThreads and ConcGCThreads equal to number of cpu cores.
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# Setting both to the same value is important to reduce STW durations.
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JVM_OPTS="$JVM_OPTS -XX:ParallelGCThreads=$system_cpu_cores -XX:ConcGCThreads=$system_cpu_cores"
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fi
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if [ "$JVM_ARCH" = "64-Bit" ] && [ $USING_CMS -eq 0 ]; then
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JVM_OPTS="$JVM_OPTS -XX:+UseCondCardMark"
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fi
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@ -183,10 +179,11 @@ JVM_OPTS="$JVM_OPTS -XX:CompileCommandFile=$CASSANDRA_CONF/hotspot_compiler"
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# add the jamm javaagent
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JVM_OPTS="$JVM_OPTS -javaagent:$CASSANDRA_HOME/lib/jamm-0.4.0.jar"
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# set jvm HeapDumpPath with CASSANDRA_HEAPDUMP_DIR
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if [ "x$CASSANDRA_HEAPDUMP_DIR" != "x" ]; then
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JVM_OPTS="$JVM_OPTS -XX:HeapDumpPath=$CASSANDRA_HEAPDUMP_DIR/cassandra-`date +%s`-pid$$.hprof"
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if [ "x$CASSANDRA_HEAPDUMP_DIR" = "x" ]; then
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CASSANDRA_HEAPDUMP_DIR="$CASSANDRA_LOG_DIR"
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fi
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JVM_OPTS="$JVM_OPTS -XX:HeapDumpPath=$CASSANDRA_HEAPDUMP_DIR/cassandra-`date +%s`-pid$$.hprof"
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# stop the jvm on OutOfMemoryError as it can result in some data corruption
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# uncomment the preferred option
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@ -160,39 +160,12 @@
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# HEAP SETTINGS #
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#################
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# Heap size is automatically calculated by cassandra-env based on this
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# formula: max(min(1/2 ram, 1024MB), min(1/4 ram, 8GB))
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# That is:
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# - calculate 1/2 ram and cap to 1024MB
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# - calculate 1/4 ram and cap to 8192MB
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# - pick the max
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# Heap size is automatically calculated by cassandra-env.sh based on the
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# formula: min(1/2 ram, CMS ? 16G : 31G)
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#
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# For production use you may wish to adjust this for your environment.
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# If that's the case, uncomment the -Xmx and Xms options below to override the
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# automatic calculation of JVM heap memory.
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#
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# It is recommended to set min (-Xms) and max (-Xmx) heap sizes to
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# the same value to avoid stop-the-world GC pauses during resize, and
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# so that we can lock the heap in memory on startup to prevent any
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# of it from being swapped out.
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#-Xms4G
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#-Xmx4G
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# If that's the case, see MAX_HEAP_SIZE (and HEAP_NEWSIZE for CMS) in cassandra-env.sh
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# Young generation size is automatically calculated by cassandra-env
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# based on this formula: min(100 * num_cores, 1/4 * heap size)
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#
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# The main trade-off for the young generation is that the larger it
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# is, the longer GC pause times will be. The shorter it is, the more
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# expensive GC will be (usually).
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#
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# It is not recommended to set the young generation size if using the
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# G1 GC, since that will override the target pause-time goal.
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# More info: http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html
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#
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# The example below assumes a modern 8-core+ machine for decent
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# times. If in doubt, and if you do not particularly want to tweak, go
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# 100 MB per physical CPU core.
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#-Xmn800M
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###################################
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# EXPIRATION DATE OVERFLOW POLICY #
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@ -50,23 +50,32 @@
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## some JVMs will fill up their heap when accessed via JMX, see CASSANDRA-6541
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##-XX:+CMSClassUnloadingEnabled
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# Young generation size
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# The main trade-off for the young generation is that the larger it is, the longer GC pause
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# times will be. The smaller it is, the more expensive GC will be (usually).
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#
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# If left unset MAX_HEAP_SIZE and HEAP_NEWSIZE in cassandra-env.sh take precedence.
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#-Xmn800M
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### G1 Settings
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## Use the Hotspot garbage-first collector.
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-XX:+UseG1GC
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-XX:+ParallelRefProcEnabled
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-XX:MaxTenuringThreshold=1
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-XX:MaxTenuringThreshold=2
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-XX:G1HeapRegionSize=16m
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#
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## Have the JVM do less remembered set work during STW, instead
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## preferring concurrent GC. Reduces p99.9 latency.
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# Floor the young generation size to 50% of the heap size
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-XX:+UnlockExperimentalVMOptions
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-XX:G1NewSizePercent=50
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# Have the JVM do less remembered set work during STW, instead
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# preferring concurrent GC. Reduces p99.9 latency.
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-XX:G1RSetUpdatingPauseTimePercent=5
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#
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## Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
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## 200ms is the JVM default and lowest viable setting
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## 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
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# Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
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# 200ms is the JVM default and lowest viable setting
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# 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
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-XX:MaxGCPauseMillis=300
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## Optional G1 Settings
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@ -77,9 +86,10 @@
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# For systems with > 8 cores, the default ParallelGCThreads is 5/8 the number of logical cores.
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# Otherwise equal to the number of cores when 8 or less.
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# Machines with > 10 cores should try setting these to <= full cores.
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#-XX:ParallelGCThreads=16
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# By default, ConcGCThreads is 1/4 of ParallelGCThreads.
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# Setting both to the same value can reduce STW durations.
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# When leaving both unset then cassandra-env.sh will set them both to the number of your cores.
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#-XX:ParallelGCThreads=16
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#-XX:ConcGCThreads=16
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@ -32,17 +32,20 @@
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## Use the Hotspot garbage-first collector.
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-XX:+UseG1GC
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-XX:+ParallelRefProcEnabled
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-XX:MaxTenuringThreshold=1
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-XX:MaxTenuringThreshold=2
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-XX:G1HeapRegionSize=16m
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#
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## Have the JVM do less remembered set work during STW, instead
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## preferring concurrent GC. Reduces p99.9 latency.
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# Floor the young generation size to 50% of the heap size
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-XX:+UnlockExperimentalVMOptions
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-XX:G1NewSizePercent=50
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# Have the JVM do less remembered set work during STW, instead
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# preferring concurrent GC. Reduces p99.9 latency.
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-XX:G1RSetUpdatingPauseTimePercent=5
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#
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## Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
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## 200ms is the JVM default and lowest viable setting
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## 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
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# Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
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# 200ms is the JVM default and lowest viable setting
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# 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
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-XX:MaxGCPauseMillis=300
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## Optional G1 Settings
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# For systems with > 8 cores, the default ParallelGCThreads is 5/8 the number of logical cores.
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# Otherwise equal to the number of cores when 8 or less.
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# Machines with > 10 cores should try setting these to <= full cores.
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#-XX:ParallelGCThreads=16
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# By default, ConcGCThreads is 1/4 of ParallelGCThreads.
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# Setting both to the same value can reduce STW durations.
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# When leaving both unset then cassandra-env.sh will set them both to the number of your cores.
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#-XX:ParallelGCThreads=16
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#-XX:ConcGCThreads=16
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