blacksmith-cache: mount git mirror sticky disk with noinit_itable - #39
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marked this pull request as ready for review
July 29, 2026 22:09
adityamaru
approved these changes
Jul 30, 2026
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Summary
The git-mirror sticky disk is formatted with
mkfs.ext4 -E lazy_itable_init=1, deferring inode-table zeroing to theext4lazyinitkernel thread that runs after mount. Git-mirror entities are our highest-clone-count, lowest-commit-rate sticky disks β their committed snapshots are typically frozen before lazy init completes, so every clone replays the same multi-GB zeroing, which is discarded with the clone and never converges. Some of the write churn we attribute to git-mirror disks is likely this phantom zeroing rather than real mirror updates.Fix: mount with
-o noinit_itableto disable the zeroing thread. It is unnecessary for correctness β mkfs enables checksummed group descriptors that track unused inodes, and unallocated blocks on the thin-provisioned RBD device read back as zeroes.Same fix as useblacksmith/stickydisk#68 and useblacksmith/setup-docker-builder#123.
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Requested by: @piob-io
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