[PATCH 0/5] A series of performance enhancements in the memihash and name-cache area

On Windows, calls to memihash() and maintaining the istate.name_hash and istate.dir_hash HashMaps take significant time on very large repositories. This series of changes reduces the overall time taken for various operations by reducing the number calls to memihash(), moving some of them into multi-threaded code, and etc.

Note: one commenter in https://github.com/git-for-windows/git/pull/964
pointed out that memihash() only handles ASCII correctly. That is true.
And fixing this is outside the purview of this patch series.

[jes: renamed and reformatted a few places, and replaced global constants by 1-bit fields, in the hopes to make the contribution a smoother ride.]

Jeff Hostetler (5):
  name-hash: eliminate duplicate memihash call
  hashmap: allow memihash computation to be continued
  name-hash: precompute hash values during preload-index
  name-hash: specify initial size for istate.dir_hash table
  name-hash: remember previous dir_entry during lazy_init_name_hash

 cache.h         |   6 +++
 hashmap.c       |  14 +++++++
 hashmap.h       |   2 +
 name-hash.c     | 116 ++++++++++++++++++++++++++++++++++++++++++++++++--------
 preload-index.c |   2 +
 read-cache.c    |   3 ++
 6 files changed, 127 insertions(+), 16 deletions(-)

base-commit: 5588dbffbd61e4906e453808c6ad32f792fea521
Published-As: https://github.com/dscho/git/releases/tag/memihash-perf-v1
Fetch-It-Via: git fetch https://github.com/dscho/git memihash-perf-v1