tame benchmark time

[vtjnash]

The tests take too long, here's why:

$ grep '^[^ ]' 093b2a6ea943f4c70fef4742453e73dd1aba255c_primary.out 
RUNNING BENCHMARKS...
(1/20) benchmarking "shootout"...
done (took 70.756991683 seconds)
(2/20) benchmarking "string"...
done (took 90.13968044 seconds)
(3/20) benchmarking "linalg"...
done (took 833.003473297 seconds)
(4/20) benchmarking "parallel"...
done (took 17.074202133 seconds)
(5/20) benchmarking "find"...
done (took 139.282557616 seconds)
(6/20) benchmarking "tuple"...
done (took 107.72978849 seconds)
(7/20) benchmarking "dates"...
done (took 112.767580891 seconds)
(8/20) benchmarking "micro"...
done (took 43.087218279 seconds)
(9/20) benchmarking "io"...
done (took 61.65084442 seconds)
(10/20) benchmarking "scalar"... # not unreasonable tests, but takes 2 seconds each
done (took 2877.452812717 seconds)
(11/20) benchmarking "sparse"... # "matmul" has over 200 combinations, probably could be more "sparse"
done (took 1278.73521643 seconds)
(12/20) benchmarking "broadcast"...
done (took 104.842238879 seconds)
(13/20) benchmarking "union"... # 341 tests may be reasonable, but taking 3 seconds each
done (took 1192.683332499 seconds)
(14/20) benchmarking "simd"...
done (took 337.777793678 seconds)
(15/20) benchmarking "random"...
done (took 619.551763952 seconds)
(16/20) benchmarking "problem"...
done (took 172.609170893 seconds)
(17/20) benchmarking "array"... # 608 "index" tests may be a bit much, and take 4 seconds each
done (took 2795.986356153 seconds)
(18/20) benchmarking "misc"...
done (took 158.855686545 seconds)
(19/20) benchmarking "sort"...
done (took 648.501236383 seconds)
(20/20) benchmarking "collection"...
done (took 916.806169471 seconds)

[KristofferC]

How about turning of the GC scrubbing (via the gctrial and gcsample in https://github.com/JuliaCI/BenchmarkTools.jl/blob/master/doc/manual.md#benchmark-parameters)? We only use the minimum value anyway for all reports and analyses.