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This document lists some points that can be improved to increase performances, generally CPU time.

Server Startup

Step	CPU Time	Reasons	Solutions
Registration of quality profiles	~37%	Bad management of SQL requests	Replace Hibernate by MyBatis and use batch insert mode Register profiles once by using the table LOADED_TEMPLATES
Registration of rules	~9%	Bad management of SQL requests	Replace Hibernate by MyBatis and use batch insert mode
Initialization of Hibernate	~8%	For information MyBatis initialization is ~3%.	Drop Hibernate
Registration of metrics	~3%	Bad management of SQL requests	Replace Hibernate by MyBatis and use batch insert mode
Initialization of JRuby on Rails	~23%	Heavily framework initialization, including ActiveRecord loading of tables metadata	Replacing JIT compilation by AOT did not help Use Java 7 invokedynamic. Upgrading to latest version of JRuby is recommended, but it requires to stop the support of Servlet 2.4 (Tomcat 5.5)

	Reasons	Solutions
Unit tests : Hibernate initialization		To be killed
Unit tests : Database startup	Derby seems to be slow to be started	Replace Derby by H2. David estimation : performances x 2. https://jira.codehaus.org/browse/SONAR-3507
Unit tests : sequential execution of tests	Some modules execute tests in parallel, but's currently not possible on the modules that start an in-memory database	TBD
Compilation : GWT		Use -Pdev to reduce number of GWT permutations Replace GWT by Ruby on Rails

	Reasons	Solutions
PMD is slow		Parallel execution of file analysis, if PMD is thread-safe

Note that integration tests are close-source and use a SonarSource internal framework to interact with Sonar components.

	Reasons	Solutions
Download, unzip, build war and deploy to cargo	Requires many filesystem I/O but not network I/O because of local cache of zip files	To be defined. Publishing a standalone and runnable WAR is a good candidate.
Server startup	See above
Server shutdown	Timeout to guarantee that queue of notifications is empty	See https://jira.codehaus.org/browse/SONAR-3509
Initialization of Selenium RC	Is the Selenium proxy long to be started ? To be verified	Test suites could use the same Selenium RC proxy http://jira.sonarsource.com/browse/ORCH-91
Too many server startups	Each Java file uses at least one server	Group unit tests by reusing shared servers. BUT this is a problem only if server startup is long.
Project inspections are long		Use the Sonar Runner instead of Maven to launch inspections Do not build sources when possible, by storing bytecode in SCM Do not execute rule engines when not needed -> should be the default behavior
Each junit test is long	Due to test requirements (server, code inspection, selenium rc)	Use parallel tests
Many tests to execute	Because we love tests	Execute only the tests that relate to changed code

	Solutions
Many HTTP requests to get images	Use CSS sprites