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Alexander Motin
dc91a6a660
- Introduce first element offset within a leaf. It allows to reduce by ~50% average memmove() size when adding/removing elements. If the added/removed element is in the first half of the leaf, we may shift elements before it and adjust the bth_first instead of moving more elements after it. - Use memcpy() instead of memmove() when we know there is no overlap. - Switch from uint64_t to uint32_t. It does not limit anything, but 32-bit arches should appreciate it greatly in hot paths. - Store leaf capacity in struct btree to avoid 64-bit divisions. - Adjust zfs_btree_insert_into_leaf() to always result in balanced leaves after splitting, no matter where the new element was inserted. Not that we care about it much, but it should also allow B-trees with as little as two elements per leaf instead of 4 previously. When scrubbing pool of 12 SSDs, storing 1.5TB of 4KB zvol blocks this reduces amount of time spent in memmove() inside the scan thread from 13.7% to 5.7% and total scrub time by ~15 seconds out of 9 minutes. It should also reduce spacemaps load time, but I haven't measured it. Reviewed-by: Paul Dagnelie <pcd@delphix.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored-By: iXsystems, Inc. Closes #13582