Parameterized jmeter threadgroup and loop count settings

as pointed out in the mailing list post,

run jmeter with user specified jmeter parameters, e.g.,

jmeter -J threads=10 -J loopcount=5

and then, in the threadgroup, set the relevant fields to, e.g.,

${__P(threads)} and ${__P(loopcount)}

In the beanshell sampler, parameters can also be accessed via:
JMeterUtils.getProperty("threads");