[jbossts-issues] [JBoss JIRA] Commented: (JBTM-555) make memory leak tests more robust

make memory leak tests more robust ---------------------------------- Key: JBTM-555 URL: https://jira.jboss.org/jira/browse/JBTM-555 Project: JBoss Transaction Manager Issue Type: Task Security Level: Public(Everyone can see) Components: Testing, Transaction Core Affects Versions: 4.6.1 Reporter: Jonathan Halliday Assignee: Jonathan Halliday Fix For: future Some tests in the txcore group attempt to detect memory leaks by setup System.gc() take memory reading doTransactionStuff System.gc() take another memory reading This is unreliable, as System.gc() is only advisory to the runtime. There is no way to FORCE gc from within the jvm. This causes the tests to be somewhat unreliable. Dirty tricks to work around this include running the tests with a small heap (-Xmx5m). With less free space to work with, the gc tries harder. On a default size heap it mostly ignores System.gc(). Unfortunately the test framework does not make it easy to set -Xmx on a per test / test group basis. Similar effect could perhaps be achieved by allocating all except a small portion of the available heap from within the vm using eg. new byte[]. There is also the jvmti ForceGarbageCollection method, but that would require us to have a chunk of C code on each test platform, which is a pain.