Introduction to Jmeter

While Controller:
While Controller Runs, its children until the condition is “false”.
Possible condition values:
•blank – exit loop when last sample in loop fails
•LAST – exit loop when last sample in loop fails. If the last sample just before the loop failed, don’t enter loop.
•Otherwise – exit (or don’t enter) the loop when the condition is equal to the string “false”

If controller:
The If Controller allows the user to control whether the test elements below it (its children) are run or not.
Examples (Variable Expression):
•${__jexl(${COUNT} < 10)}
•${RESULT}

Runtime Controller:
The Runtime Controller controls how long its children are allowed to run.