Hi, vr

The 1.5 - 2 seconds is likely threads freeing memory. Change my %cache to our %cache. MCE defaults to spawning threads on Windows. Try passing the MCE option use_threads => 0 to ensure emulated child instead.

our %cache = ( 1 => [ 1, 1, undef ]);  # for faster global cleanup

mce_flow_s {
    max_workers => MCE::Util::get_ncpu(),
    gather      => \@sizes,
    bounds_only => 1,
    use_threads => 0,
}, sub {
    …
}, 1, 1e6;
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