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RDD Cache PMem Extension

Contents

Introduciton

OAP Spark support RDD Cache with Optane PMem. Spark has various storage levels serving for different purposes including memory and disk.

PMem storage level is added to support a new tier for storage level besides memory and disk.

Using PMem library to access Optane PMem can help to avoid the overhead from disk.

Large capacity and high I/O performance of PMem shows better performance than tied DRAM and disk solution under the same cost.

User Guide

Prerequisites

The following are required to configure OAP to use PMem cache in AppDirect mode.

  • PMem hardware is successfully deployed on each node in cluster.

  • Directories exposing PMem hardware on each socket. For example, on a two socket system the mounted PMem directories should appear as /mnt/pmem0 and /mnt/pmem1. Correctly installed PMem must be formatted and mounted on every cluster worker node.

    // use ipmctl command to show topology and dimm info of PMem
ipmctl show -topology
ipmctl show -dimm
// provision PMem in app direct mode
ipmctl create -goal PersistentMemoryType=AppDirect
// reboot system to make configuration take affect
reboot
// check capacity provisioned for app direct mode(AppDirectCapacity)
ipmctl show -memoryresources
// show the PMem region information
ipmctl show -region
// create namespace based on the region, multi namespaces can be created on a single region
ndctl create-namespace -m fsdax -r region0
ndctl create-namespace -m fsdax -r region1
// show the created namespaces
fdisk -l
// create and mount file system
echo y | mkfs.ext4 /dev/pmem0
echo y | mkfs.ext4 /dev/pmem1
mount -o dax /dev/pmem0 /mnt/pmem0
mount -o dax /dev/pmem1 /mnt/pmem1

    In this case file systems are generated for 2 numa nodes, which can be checked by "numactl --hardware". For a different number of numa nodes, a corresponding number of namespaces should be created to assure correct file system paths mapping to numa nodes.

  • Make sure Memkind library installed on every cluster worker node. Compile Memkind based on your system or directly place our pre-built binary of libmemkind.so.0 for x86 64bit CentOS Linux in the /lib64/directory of each worker node in cluster. The Memkind library depends on libnuma at the runtime, so it must already exist in the worker node system. Build the latest memkind lib from source:

    git clone -b v1.10.1-rc2 https://github.com/memkind/memkind
cd memkind
./autogen.sh
./configure
make
make install

  • For KMem Dax mode, we need to configure PMem as system ram. Kernel 5.1 or above is required to this mode.

    daxctl migrate-device-model
ndctl create-namespace --mode=devdax --map=mem
ndctl list
daxctl reconfigure-device dax0.0 --mode=system-ram
daxctl reconfigure-device dax1.0 --mode=system-ram
daxctl reconfigure-device daxX.Y --mode=system-ram

Refer Memkind KMem for details.

Compiling

To build oap spark and oap common, you can run below commands:

cd ${OAP_CODE_HOME}
mvn clean package -Ppersistent-memory -DskipTests

You will find jar files under oap-common/target and oap-spark/target.

Configuration

To enable rdd cache on Intel Optane PMem, you need add the following configurations to spark-defaults.conf

spark.memory.pmem.initial.path [Your Optane PMem paths seperate with comma]
spark.memory.pmem.initial.size [Your Optane PMem size in GB]
spark.memory.pmem.usable.ratio [from 0 to 1, 0.85 is recommended]
spark.yarn.numa.enabled true
spark.yarn.numa.num [Your numa node number]
spark.memory.pmem.mode [AppDirect | KMemDax]

spark.files                       file://${PATH_TO_OAP_SPARK_JAR}/oap-spark-<version>-with-spark-<version>.jar,file://${{PATH_TO_OAP_COMMON_JAR}/oap-common-<version>-with-spark-<version>.jar
spark.executor.extraClassPath     ./oap-spark-<version>-with-spark-<version>.jar:./oap-common-<version>-with-spark-<version>.jar
spark.driver.extraClassPath       file://${PATH_TO_OAP_SPARK_JAR}/oap-spark-<version>-with-spark-<version>.jar:file://${{PATH_TO_OAP_COMMON_JAR}/oap-common-<version>-with-spark-<version>.jar

Use Optane PMem to cache data

There's a new StorageLevel: PMEM_AND_DISK being added to cache data to Optane PMem, at the places you previously cache/persist data to memory, use PMEM_AND_DISK to substitute the previous StorageLevel, data will be cached to Optane PMem.

persist(StorageLevel.PMEM_AND_DISK)

Run K-means benchmark

You can use Hibench to run K-means workload:

After you Build Hibench, then follow Run SparkBench documentation. Here are some tips besides this documentation you need to notice. Follow the documentation to configure these 4 files:

HiBench/conf/hadoop.conf
HiBench/conf/hibench.conf
HiBench/conf/spark.conf
HiBench/conf/workloads/ml/kmeans.conf

Note that you need add hibench.kmeans.storage.level PMEM_AND_DISK to kmeans.conf, which can enable both PMem and Disk to cache data. Then you can run the following 2 commands to run K-means workloads:

bin/workloads/ml/kmeans/prepare/prepare.sh
bin/workloads/ml/kmeans/spark/run.sh

Then you can find the log as below:

patching args=
Parsing conf: /home/wh/HiBench/conf/hadoop.conf
Parsing conf: /home/wh/HiBench/conf/hibench.conf
Parsing conf: /home/wh/HiBench/conf/spark.conf
Parsing conf: /home/wh/HiBench/conf/workloads/ml/kmeans.conf
probe sleep jar: /opt/Beaver/hadoop/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-2.7.3-tests.jar
start ScalaSparkKmeans bench
hdfs rm -r: /opt/Beaver/hadoop/bin/hadoop --config /opt/Beaver/hadoop/etc/hadoop fs -rm -r -skipTrash hdfs://vsr219:9000/HiBench/Kmeans/Output
rm: `hdfs://vsr219:9000/HiBench/Kmeans/Output': No such file or directory
hdfs du -s: /opt/Beaver/hadoop/bin/hadoop --config /opt/Beaver/hadoop/etc/hadoop fs -du -s hdfs://vsr219:9000/HiBench/Kmeans/Input
Export env: SPARKBENCH_PROPERTIES_FILES=/home/wh/HiBench/report/kmeans/spark/conf/sparkbench/sparkbench.conf
Export env: HADOOP_CONF_DIR=/opt/Beaver/hadoop/etc/hadoop
Submit Spark job: /opt/Beaver/spark/bin/spark-submit  --properties-file /home/wh/HiBench/report/kmeans/spark/conf/sparkbench/spark.conf --class com.intel.hibench.sparkbench.ml.DenseKMeans --master yarn-client --num-executors 2 --executor-cores 45 --executor-memory 100g /home/wh/HiBench/sparkbench/assembly/target/sparkbench-assembly-8.0-SNAPSHOT-dist.jar -k 10 --numIterations 5 --storageLevel PMEM_AND_DISK hdfs://vsr219:9000/HiBench/Kmeans/Input/samples
20/07/03 09:07:49 INFO util.ShutdownHookManager: Deleting directory /tmp/spark-43459116-f4e3-4fe1-bb29-9bca0afa5286
finish ScalaSparkKmeans bench

Open the Spark History Web UI and go to the Storage tab page to verify the cache metrics.

Limitations

For the scenario that data will exceed the block cache capacity. Memkind 1.9.0 and kernel 4.18 is recommended to avoid the unexpected issue.

How to contribute

OAP Spark packages includes all Spark changed files. All codes are directly copied from https://github.com/Intel-bigdata/Spark. Please make sure all your changes are committed to the repository above. Otherwise, your change will be override by others.

The files from this package should avoid depending on other OAP module except OAP-Common.

All Spark source code changes are tracked in dev/changes_list/spark_changed_files

All changed files are ordered by file name.

You can execute the script dev/Apply_Spark_changes.sh with the specified Spark source directories and OAP source directories accordingly.