On Wed, 5 Aug 2009, Linus Torvalds wrote:
>
> Timings for "git fsck --full" on the git directory:
>
> - Mozilla SHA1 portable C-code (sucky sucky): MOZILLA_SHA1=1
>
> real 0m38.194s
> user 0m37.838s
> sys 0m0.356s
>
> - This code ("half-portable C code"): BLK_SHA1=1
>
> real 0m28.120s
> user 0m27.930s
> sys 0m0.192s
>
> - OpenSSL assembler code:
>
> real 0m26.327s
> user 0m26.194s
> sys 0m0.136s
Ok, I installed the 32-bit libraries too, to see what it looks like for
that case. As expected, the compiler is not able to do a great job due to
it being somewhat register starved, but on the other hand, the old Mozilla
code did even worse, so..
- Mozilla SHA:
real 0m47.063s
user 0m46.815s
sys 0m0.252s
- BLK_SHA1=1
real 0m34.705s
user 0m34.394s
sys 0m0.312s
- OPENSSL:
real 0m29.754s
user 0m29.446s
sys 0m0.288s
so the tuned asm from OpenSSL does kick ass, but the C code version isn't
_that_ far away. It's quite a reasonable alternative if you don't have the
OpenSSL libraries installed, for example.
I note that MINGW does NO_OPENSSL by default, for example, and maybe the
MINGW people want to test the patch out and enable BLK_SHA1 rather than
the original Mozilla one.
But while looking at 32-bit issues, I noticed that I really should also
cast 'len' when shifting it. Otherwise the thing is limited to fairly
small areas (28 bits - 256MB). This is not just a 32-bit problem ("int" is
a signed 32-bit thing even in a 64-bit build), but I only noticed it when
looking at 32-bit issues.
So here's an incremental patch to fix that.
Linus
---
block-sha1/sha1.c | 4 ++--
block-sha1/sha1.h | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index 8fd90b0..eef32f7 100644
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -27,11 +27,11 @@ void blk_SHA1_Init(blk_SHA_CTX *ctx)
}
-void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, int len)
+void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
{
int lenW = ctx->lenW;
- ctx->size += len << 3;
+ ctx->size += (unsigned long long) len << 3;
/* Read the data into W and process blocks as they get full
*/
diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h
index dbc719f..7be2d93 100644
--- a/block-sha1/sha1.h
+++ b/block-sha1/sha1.h
@@ -12,7 +12,7 @@ typedef struct {
} blk_SHA_CTX;
void blk_SHA1_Init(blk_SHA_CTX *ctx);
-void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, int len);
+void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, unsigned long len);
void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
#define git_SHA_CTX blk_SHA_CTX
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