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power-of-two page block it frees, launching an unsuccessful search for a buddy to pair up with each time. The only possible buddy-up mergers are across the boundaries of the freed region, so change vm_phys_free_contig simply to enqueue the freed interior blocks, via a new function vm_phys_enqueue_contig, and then call vm_phys_free_pages on the bounding blocks to create as big a cross-boundary block as possible after buddy-merging. The only callers of vm_phys_free_contig at the moment call it in situations where merging blocks across the boundary is clearly impossible, so just call vm_phys_enqueue_contig in those places and avoid trying to buddy-up at all. One beneficiary of this change is in breaking reservations. For the case where memory is freed in breaking a reservation with only the first and last pages allocated, the number of cycles consumed by the operation drops about 11% with this change. Suggested by: alc Reviewed by: alc Approved by: kib, markj (mentors) Differential Revision: https://reviews.freebsd.org/D16901
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