mw::SchedulerTestFixture::testPeriod10HzNoPayloadChaffX4 fails more often than not

The stats are all reported in microseconds, and the test is currently set to fail if any event happens more than 1 millisecond late, which might be too aggressive on most machines.

However, it does look like something is amiss. In January, on this same laptop, I clocked the following scheduler benchmarks:

testPeriod10HzNoPayload ----------> 99.25% of runs < 100us latency; 100% < 500us
testPeriod100HzNoPayload: --------> 99.75% of runs < 100us latency; 100% < 500us
testPeriod10HzNoPayloadChaffX4: --> 99.50% of runs < 100us latency; 2 faults > 1ms
testPeriod10HzSmallPayload: ------> 97.24% of runs < 100us latency; 100% < 500us
testOneOffFiringSmallPayload:   ----> 100% of runs < 500us latency

Today:

testPeriod10HzNoPayload: ---------> 99.75% < 100us; 100% < 500us
testPeriod100HzNoPayload: --------> 100% < 100us
testPeriod10HzNoPayloadChaffX4:--> 94.21% < 1000us; 97.23% < 15000us 
testPeriod10HzSmallPayload:-------> 100% < 500us
testOneOffFiringSmallPayload: ----> 100% < 500us

So, the chaff test has always been the hardest, but something going very wrong relative to before, though the rest of the tests look basically normal. Those January benchmarks were collected under 10.6, but maybe something changed in the scheduler in an update? It would be helpful to run this test across a variety of different OS / hardware combinations to see if a pattern emerges.

I also wonder if the problem has more to do with the chaff threads than the scheduled payload -- on my machine the chaff threads are doing a very good job of saturating the CPU cores (occasionally, the Activity Monitor reads numbers > 200% for the test runner, which is weird).