Avoid re-marking ephemerons with trivial data - #13827
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Full GC logs corresponding to 5.3.0 and this PR, with timings (in s): GC-full-530.txt -> 11.7287089825 By comparison, the 4.14 time is 6.33123278618. |
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Code is correct; naming quibbles.
In general, ephemerons may need to be marked more than once, if new marking has occurred since ephemeron marking began. This patch optimises this logic: re-marking is never necessary if the data field of the ephemeron is trivial. This optimisation was present in OCaml 4, and is important for Stdlib.Weak, which only uses ephemerons with trivial data.
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In general, ephemerons may need to be marked more than once, if new marking has occurred since ephemeron marking began. This patch optimises this logic: re-marking is never necessary if the data field of the ephemeron is trivial. This optimisation was present in OCaml 4, and is important for Stdlib.Weak, which only uses ephemerons with trivial data.
This means that programs using
Weakwill only do one pass over the ephemeron set, since the ephemerons backing weak tables will be removed from the todo list once they are scanned.cc @nojb who's interested in testing this: could you report the
OCAMLRUNPARAM=v=0xfffGC logs on your test case before and after this patch, as well as timings?