perf: allocate a chain's sectors for a whole write at once - #86
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francisdb wants to merge 2 commits into
Open
perf: allocate a chain's sectors for a whole write at once#86francisdb wants to merge 2 commits into
francisdb wants to merge 2 commits into
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Chains went through the underlying reader or writer one sector per call. Consecutive sectors are now read or written in a single call.
A write now allocates all the sectors it needs first, writes their FAT entries together, and skips zeroing sectors it fills completely.
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Builds on #85 (its commit is included here until it merges).
Growing a chain cost a FAT entry write for the new sector, another to link it, and a zero fill, per sector. A write past the end of a chain now takes all the sectors it needs first (
Allocator::extend_chain_by), writes the FAT entries of each run of consecutive ids together, and skips the zero fill of sectors it fills completely; the unused tail of the last sector andset_lengrowth are still zeroed.