[PATCH v5 0/4] read-cache: speed up add_index_entry

From: Jeff Hostetler <jeffhost@microsoft.com>

[This is labeled as version 5 because of a cut-n-paste accident where my first version of this patch was labeled version 4.]

This version adds more perf tests to p0004-read-tree.sh

================ Teach add_index_entry_with_check() and has_dir_name() to avoid index lookups if the given path sorts after the last entry in the index.

This saves at least 2 binary searches per entry.

This improves performance during checkout and read-tree because merge_working_tree() and unpack_trees() processes a list of already sorted entries.

This helps performance on very large repositories.

================ Before and after numbers on index with 1M files ./p0004-read-tree.sh 0004.2: read-tree work1 (1003037) 3.21(2.54+0.62) 0004.3: switch base work1 (3038 1003037) 7.49(5.39+1.84) 0004.5: switch work1 work2 (1003037) 11.91(8.38+3.00) 0004.6: switch commit aliases (1003037) 12.22(8.30+3.06)

./p0004-read-tree.sh 0004.2: read-tree work1 (1003040) 2.40(1.65+0.73) 0004.3: switch base work1 (3041 1003040) 6.07(4.12+1.66) 0004.5: switch work1 work2 (1003040) 10.23(6.76+2.92) 0004.6: switch commit aliases (1003040) 10.53(6.97+2.83) ================

Jeff Hostetler (4):
  p0004-read-tree: perf test to time read-tree
  read-cache: add strcmp_offset function
  test-strcmp-offset: created test for strcmp_offset
  read-cache: speed up add_index_entry during checkout

 Makefile                      |   1 +
 cache.h                       |   1 +
 read-cache.c                  |  73 +++++++++++++++++++++++++-
 t/helper/.gitignore           |   1 +
 t/helper/test-strcmp-offset.c |  64 +++++++++++++++++++++++
 t/perf/p0004-read-tree.sh     | 116 ++++++++++++++++++++++++++++++++++++++++++
 t/t0065-strcmp-offset.sh      |  11 ++++
 7 files changed, 266 insertions(+), 1 deletion(-)
 create mode 100644 t/helper/test-strcmp-offset.c
 create mode 100755 t/perf/p0004-read-tree.sh
 create mode 100755 t/t0065-strcmp-offset.sh