HSEARCH-3827 Copy the README for backend performance tests from Searc…

…h 5 and adapt it

integrationtest/performance/backend/README.md

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+# Backend Performance tests
+
+This module is designed to verify throughput of the document creation and indexing.
+
+This module is decoupled from any mapper to allow running performance diagnostics
+and find regressions in isolation from the various mappers.
+
+## Build
+
+To build the performance tests:
+
+```
+mvn clean install -pl integrationtest/performance/backend/elasticsearch -am -DskipTests
+# OR
+mvn clean install -pl integrationtest/performance/backend/lucene -am -DskipTests
+```
+
+## Run it from command line with standard jars
+
+To run the benchmarks:
+
+## Run it from command line
+
+There is an alternative way to run it which might be handy when needing to copy the
+performance test to a dedicated server and for some reason you're not liking rsync:
+
+```
+java -jar integrationtest/performance/backend/elasticsearch/target/benchmarks.jar
+# OR
+java -jar integrationtest/performance/backend/lucene/target/benchmarks.jar
+```
+
+You may set parameters:
+
+```
+java -jar integrationtest/performance/backend/elasticsearch/benchmarks.jar \
+    -jvmArgsPrepend -Dhosts=es1.mycompany.com \
+    -jvmArgsPrepend -Dprotocol=https \
+    -i 10 -p batchSize=50
+```
+
+* `jvmArgsPrepend`: add additional JVM properties to the forked process which runs the benchmark.
+Note that this can be used to override backend properties, such as the Elasticsearch hosts in this example.
+* `e`: excludes running all benchmarks matching this name.
+* `w`: sets the number of warm-up iterations.
+* `i`: sets the number of measurement iterations.
+* `p`: set testing parameters (`@Param` in the code).
+
+## Run it from your IDE
+
+Within your IDE, run the test `SmokeIT` located in the project you're interested in.
+
+## Run flight recorder: long runs on a specific test
+
+```
+java -jar integrationtest/performance/backend/elasticsearch/benchmarks.jar \
+    -jvmArgsPrepend -XX:+FlightRecorder \
+    -i 30000
+```
+
+We're setting it a very high number of iterations here to have time to play with
+Flight Recorder before it shuts down.
+
+You can also dump the result to a .jfr file and study it later (useful to run it on a remote server):
+
+```
+java -jar integrationtest/performance/backend/elasticsearch/benchmarks.jar \
+    -jvmArgsPrepend -XX:+FlightRecorder \
+    -jvmArgsPrepend -XX:StartFlightRecording=filename=output/profile.jfr,settings=profile
+```
+
+## Produce GC logs suited for tools
+
+```
+java -jar target/benchmarks.jar \
+    -jvmArgsPrepend "-Xloggc:lognameHere.log -XX:+PrintGCDetails -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCCause" \
+    -i 30000
+```
+
+# Notes
+
+For best results disable features such as power management, dynamic CPU scaling,
+and run it on a dedicated box which has no other significant services running.
+
+In particular the "run it from your IDE" approach is just meant for development of new tests.
+
+## TODO
+
+- add more tests, especially those focusing on backend performance
+- add search tests