Isolating tests from general concurrency

[Jonathan Gibbons]

On 3/19/19 2:34 PM, Igor Ignatyev wrote:
>> How is the queue managed when normally concurrent tests are launched?
>> Instead of waiting til the end, a test requiring concurrency=1 could simply wait
>> for the queue to drain before being launched.
> I'll let Jon to comment on the current implementation. but waiting for the queue to drain each time we meet 'nonconcurrent' test will add multiple serialization points and might have measurable impact on overall execution time.

Currently, jtreg uses the test runner mechanism provided by the 
underlying JT Harness framework.   Changing that will be a Very Big Deal.

How many nonconcurrent tests are there, out of how many tests total?

-- Jon