Does it help to wait before reattaching?
Revert the map/unmap dance I tried in commit
73042b8d1; that helps
not at all.
Instead, speculate that the unwanted allocation is being done on
another thread, and thus timing variations explain the apparent
unpredictability. Temporarily add a 1-second sleep before the
VirtualFree call, in hopes that any such other threads will
quiesce and not jog our elbow.
This is obviously not a desirable long-term fix, but as a means of
investigation it seems useful.
Discussion: https://postgr.es/m/25495.
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