lib/sha1: use the git implementation of SHA-1
For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem. The speed of the kernel sha-1 implementation has a major
impact on our boot performance.
To improve boot performance, we investigated using the heavily optimized
sha-1 implementation used in git. With the git sha-1 implementation, we
see a 11.7% improvement in boot time.
10 reboots, remove slowest/fastest.
Before:
Mean: 6.58 seconds Stdev: 0.14
After (with git sha-1, this patch):
Mean: 5.89 seconds Stdev: 0.07
The other cool thing about the git SHA-1 implementation is that it only
needs 64 bytes of stack for the workspace while the original kernel
implementation needed 320 bytes.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Cc: Nicolas Pitre <nico@cam.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cryptohash.h b/include/linux/cryptohash.h
index ec78a4b..f945218 100644
--- a/include/linux/cryptohash.h
+++ b/include/linux/cryptohash.h
@@ -3,7 +3,7 @@
#define SHA_DIGEST_WORDS 5
#define SHA_MESSAGE_BYTES (512 /*bits*/ / 8)
-#define SHA_WORKSPACE_WORDS 80
+#define SHA_WORKSPACE_WORDS 16
void sha_init(__u32 *buf);
void sha_transform(__u32 *digest, const char *data, __u32 *W);