[PATCH] mingw: use OpenSSL's SHA-1 routines

[Johannes Schindelin <johannes.schindelin@gmx.de>]

From: Jeff Hostetler <jeffhost@microsoft.com>

Use OpenSSL's SHA-1 routines rather than builtin block-sha1 routines.
This improves performance on SHA1 operations on Intel processors.

OpenSSL 1.0.2 has made considerable performance improvements and
support the Intel hardware acceleration features.  See:
https://software.intel.com/en-us/articles/improving-openssl-performance
https://software.intel.com/en-us/articles/intel-sha-extensions

To test this I added/staged a single file in a gigantic
repository having a 450MB index file.  The code in read-cache.c
verifies the header SHA as it reads the index and computes a new
header SHA as it writes out the new index.  Therefore, in this test
the SHA code must process 900MB of data.  Testing was done on an
Intel I7-4770 CPU @ 3.40GHz (Intel64, Family 6, Model 60) CPU.

The block-sha1 version averaged 5.27 seconds.
The OpenSSL    version averaged 4.50 seconds.

================================================================

$ echo xxx >> project.mk
$ time /e/blk_sha/bin/git.exe add project.mk

real    0m5.207s
user    0m0.000s
sys     0m0.250s

$ echo xxx >> project.mk
$ time /e/blk_sha/bin/git.exe add project.mk

real    0m5.362s
user    0m0.015s
sys     0m0.234s

$ echo xxx >> project.mk
$ time /e/blk_sha/bin/git.exe add project.mk

real    0m5.300s
user    0m0.016s
sys     0m0.250s

$ echo xxx >> project.mk
$ time /e/blk_sha/bin/git.exe add project.mk

real    0m5.216s
user    0m0.000s
sys     0m0.250s

================================================================
$ echo xxx >> project.mk
$ time /e/openssl/bin/git.exe add project.mk

real    0m4.431s
user    0m0.000s
sys     0m0.250s

$ echo xxx >> project.mk
$ time /e/openssl/bin/git.exe add project.mk

real    0m4.478s
user    0m0.000s
sys     0m0.265s

$ echo xxx >> project.mk
$ time /e/openssl/bin/git.exe add project.mk

real    0m4.690s
user    0m0.000s
sys     0m0.250s

$ echo xxx >> project.mk
$ time /e/openssl/bin/git.exe add project.mk

real    0m4.420s
user    0m0.000s
sys     0m0.234s

================================================================

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
Published-As: https://github.com/dscho/git/releases/tag/mingw-openssl-sha1-v1
Fetch-It-Via: git fetch https://github.com/dscho/git mingw-openssl-sha1-v1

 config.mak.uname | 1 -
 1 file changed, 1 deletion(-)

diff --git a/config.mak.uname b/config.mak.uname
index 447f36ac2e..a07936da8b 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -515,7 +515,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	OBJECT_CREATION_USES_RENAMES = UnfortunatelyNeedsTo
 	NO_REGEX = YesPlease
 	NO_PYTHON = YesPlease
-	BLK_SHA1 = YesPlease
 	ETAGS_TARGET = ETAGS
 	NO_INET_PTON = YesPlease
 	NO_INET_NTOP = YesPlease

base-commit: 6e3a7b3398559305c7a239a42e447c21a8f39ff8
-- 
2.11.1.windows.1