Zach Brown f9ff25db23 scoutfs: add dirent name fingerprint ...

Entries in a directory are indexed by the hash of their name.  This
introduces a perfectly random access pattern.  And this results in a cow
storm as directories get large enough such that the leaf blocks that
store their entries are larger than our commits.  Each commit ends up
being full of cowed leaf blocks that contain a single new entry.

The dirent name fingerprints change the dirent key to first start with a
fingerprint of the name.  This reduces the scope of hash randomization
from the entire directory to entries with the same fingerprint.

On real customer dir sizes and file names we saw roughly 3x create rate
improvements from being able to create more entries in leaf blocks
within a commit.

Signed-off-by: Zach Brown <zab@versity.com>

2020-08-26 14:39:12 -07:00

kmod

scoutfs: add dirent name fingerprint

2020-08-26 14:39:12 -07:00

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