c10aea724f
Previous code used 4 atomics to do aggsum_flush_bucket() and 2 more to re-borrow after the flush. But since asc_borrowed and asc_delta are accessed only while holding asc_lock, it makes no any sense to modify as_lower_bound and as_upper_bound in multiple steps. Instead of that the new code uses only 2 atomics in all the cases, one per as_*_bound variable. I think even that is overkill, simple atomic store and load could be used here, since all modifications are done under the as_lock, but there are no such primitives in ZFS code now. While there, make borrow code consider previous borrow value, so that on mixed request patterns reduce chance of needing to borrow again if much larger request follows tiny one that needed borrow. Also reduce as_numbuckets from uint64_t to u_int. It makes no sense to use so large division operation on every aggsum_add(). Reviewed by: Brian Behlendorf, Paul Dagnelie MFC after: 2 weeks Sponsored by: iXsystems, Inc.
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