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Commit Graph

6 Commits

Author SHA1 Message Date
Zdenek Kabelac
ff21723512 hash: replace hash with better function
Add Bob Jenkins hash function to get better working hash function,
which does genarate way less colisions (especially with similar
strings).

For a comparision also a kernel function used in DM kernel is include.
While it's better then our existing one, it's still far worse,
then Bob Jenkins hash.
2021-03-08 15:33:15 +01:00
Zdenek Kabelac
d602837b91 hash: speed up hash tables
Enhance hash perfomance by remembering the computed
hash value for the hashed node - this allows to speedup
lookup of nodes with the hash collision when
different keys map to the same masked hash value.

For the easier use 'num_slots' become 'mask_slots',
so we only add '1' in rare case of need of the original
num_slots value.

Also add statistic counters for hashes and print stats in
debug build (-DDEBUG) on hash wiping.
(so badly performing hash can be optimized.)
2021-03-08 15:33:15 +01:00
Zdenek Kabelac
84679d254f hash: use unsigned size
There is not much point in using 64bit hash size, since we hash
with way less bits anyway. So keep size 32bit.
2021-03-08 15:33:15 +01:00
Zdenek Kabelac
1ff1e86deb cleanup: better expressing passing key arg to _hash 2020-09-01 17:57:50 +02:00
Zdenek Kabelac
fd96f1014b gcc: zero-sized array to fexlible array C99
Switch remaining zero sized struct to flexible arrays to be C99
complient.

These simple rules should apply:

- The incomplete array type must be the last element within the structure.
- There cannot be an array of structures that contain a flexible array member.
- Structures that contain a flexible array member cannot be used as a member of another structure.
- The structure must contain at least one named member in addition to the flexible array member.

Although some of the code pieces should be still improved.
2020-09-01 17:57:50 +02:00
Joe Thornber
61e67e51e1 device_mapper: move hash.[hc] to base/data-struct 2018-06-08 13:54:19 +01:00