Merge pull request #450 from ruby/rmf-performance #1538

Job	Run time
benchmark-default (head)	10m 45s
test (head)	53s
benchmark-default (ruby)	10m 53s
benchmark-default (truffleruby)	11m 21s
test (truffleruby)	54s
test (ruby)	1m 5s
benchmark-ractor (ruby)	12m 48s
benchmark-graph	51s
benchmark-ractor-only (ruby)	53s
benchmark-ractor-only (head)	47s
benchmark-run-once	1m 24s
benchmark-ractor (head)	11m 55s
all-tests	2s
	1h 4m 31s

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