With a Concurrency Limit (containerCap) limit set jobs queue as expected. However, as jobs finish the queued jobs do not execute in FIFO order. If I am not mistaken they appear to be executed in ASCII Sort of the job Name…
With a concurrency limit of 3, I kicked off 11 jobs (using the Build Now button) and they executed in the following order…
1,2,3,10,11,4,5,6,7,8,9
the same issue (when waiting for free resources, e.g. RAM or CPU). To me it looks like the Jenkins scheduling is completely skipped while the order in which they are actually getting executed seems to be more or less random. Depending on which one asks first after the resources became available.