git.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Artur Skawina <art.08.09@gmail.com>
Cc: Nicolas Pitre <nico@cam.org>, George Spelvin <linux@horizon.com>,
	Junio C Hamano <gitster@pobox.com>,
	git@vger.kernel.org
Subject: Re: x86 SHA1: Faster than OpenSSL
Date: Wed, 5 Aug 2009 20:48:20 -0700 (PDT)	[thread overview]
Message-ID: <alpine.LFD.2.01.0908052043082.3390@localhost.localdomain> (raw)
In-Reply-To: <alpine.LFD.2.01.0908052024081.3390@localhost.localdomain>



On Wed, 5 Aug 2009, Linus Torvalds wrote:
> 
> However, right now my biggest profile hit is on this irritating loop:
> 
> 	/* Unroll it? */
> 	for (t = 16; t <= 79; t++)
> 		W[t] = SHA_ROL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);
> 
> and I haven't been able to move _that_ into the other iterations yet.

Oh yes I have.

Here's the patch that gets me sub-28s git-fsck times. In fact, it gives me 
sub-27s times. In fact, it's really close to the OpenSSL times.

And all using plain C.

Again - this is all on x86-64. I suspect 32-bit code ends up having 
spills due to register pressure. That said, I did get rid of that big 
temporary array, and it now basically only uses that 512-bit array as one 
circular queue.

		Linus

PS. Ok, so my definition of "plain C" is a bit odd. There's nothing plain 
about it. It's disgusting C preprocessor misuse. But dang, it's kind of 
fun to abuse the compiler this way.

---
 block-sha1/sha1.c |   28 ++++++++++++++++------------
 1 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index 39a5bbb..80193d4 100644
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -96,9 +96,8 @@ void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
 
 static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data)
 {
-	int t;
 	unsigned int A,B,C,D,E,TEMP;
-	unsigned int W[80];
+	unsigned int array[16];
 
 	A = ctx->H[0];
 	B = ctx->H[1];
@@ -107,8 +106,8 @@ static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data)
 	E = ctx->H[4];
 
 #define T_0_15(t) \
-	TEMP = htonl(data[t]); W[t] = TEMP; \
-	TEMP += SHA_ROL(A,5) + (((C^D)&B)^D)     + E + 0x5a827999; \
+	TEMP = htonl(data[t]); array[t] = TEMP; \
+	TEMP += SHA_ROL(A,5) + (((C^D)&B)^D) + E + 0x5a827999; \
 	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP; \
 
 	T_0_15( 0); T_0_15( 1); T_0_15( 2); T_0_15( 3); T_0_15( 4);
@@ -116,18 +115,21 @@ static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data)
 	T_0_15(10); T_0_15(11); T_0_15(12); T_0_15(13); T_0_15(14);
 	T_0_15(15);
 
-	/* Unroll it? */
-	for (t = 16; t <= 79; t++)
-		W[t] = SHA_ROL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);
+/* This "rolls" over the 512-bit array */
+#define W(x) (array[(x)&15])
+#define SHA_XOR(t) \
+	TEMP = SHA_ROL(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1); W(t) = TEMP;
 
 #define T_16_19(t) \
-	TEMP = SHA_ROL(A,5) + (((C^D)&B)^D)     + E + W[t] + 0x5a827999; \
-	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP;
+	SHA_XOR(t); \
+	TEMP += SHA_ROL(A,5) + (((C^D)&B)^D) + E + 0x5a827999; \
+	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP; \
 
 	T_16_19(16); T_16_19(17); T_16_19(18); T_16_19(19);
 
 #define T_20_39(t) \
-	TEMP = SHA_ROL(A,5) + (B^C^D)           + E + W[t] + 0x6ed9eba1; \
+	SHA_XOR(t); \
+	TEMP += SHA_ROL(A,5) + (B^C^D) + E + 0x6ed9eba1; \
 	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP;
 
 	T_20_39(20); T_20_39(21); T_20_39(22); T_20_39(23); T_20_39(24);
@@ -136,7 +138,8 @@ static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data)
 	T_20_39(35); T_20_39(36); T_20_39(37); T_20_39(38); T_20_39(39);
 
 #define T_40_59(t) \
-	TEMP = SHA_ROL(A,5) + ((B&C)|(D&(B|C))) + E + W[t] + 0x8f1bbcdc; \
+	SHA_XOR(t); \
+	TEMP += SHA_ROL(A,5) + ((B&C)|(D&(B|C))) + E + 0x8f1bbcdc; \
 	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP;
 
 	T_40_59(40); T_40_59(41); T_40_59(42); T_40_59(43); T_40_59(44);
@@ -145,7 +148,8 @@ static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data)
 	T_40_59(55); T_40_59(56); T_40_59(57); T_40_59(58); T_40_59(59);
 
 #define T_60_79(t) \
-	TEMP = SHA_ROL(A,5) + (B^C^D)           + E + W[t] + 0xca62c1d6; \
+	SHA_XOR(t); \
+	TEMP += SHA_ROL(A,5) + (B^C^D) + E + 0xca62c1d6; \
 	E = D; D = C; C = SHA_ROR(B, 2); B = A; A = TEMP;
 
 	T_60_79(60); T_60_79(61); T_60_79(62); T_60_79(63); T_60_79(64);

  reply	other threads:[~2009-08-06  3:49 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-26 23:21 Performance issue of 'git branch' George Spelvin
2009-07-31 10:46 ` Request for benchmarking: x86 SHA1 code George Spelvin
2009-07-31 11:11   ` Erik Faye-Lund
2009-07-31 11:31     ` George Spelvin
2009-07-31 11:37     ` Michael J Gruber
2009-07-31 12:24       ` Erik Faye-Lund
2009-07-31 12:29         ` Johannes Schindelin
2009-07-31 12:32         ` George Spelvin
2009-07-31 12:45           ` Erik Faye-Lund
2009-07-31 13:02             ` George Spelvin
2009-07-31 11:21   ` Michael J Gruber
2009-07-31 11:26   ` Michael J Gruber
2009-07-31 12:31   ` Carlos R. Mafra
2009-07-31 13:27   ` Brian Ristuccia
2009-07-31 14:05     ` George Spelvin
2009-07-31 13:27   ` Jakub Narebski
2009-07-31 15:05   ` Peter Harris
2009-07-31 15:22   ` Peter Harris
2009-08-03  3:47   ` x86 SHA1: Faster than OpenSSL George Spelvin
2009-08-03  7:36     ` Jonathan del Strother
2009-08-04  1:40     ` Mark Lodato
2009-08-04  2:30     ` Linus Torvalds
2009-08-04  2:51       ` Linus Torvalds
2009-08-04  3:07         ` Jon Smirl
2009-08-04  5:01           ` George Spelvin
2009-08-04 12:56             ` Jon Smirl
2009-08-04 14:29               ` Dmitry Potapov
2009-08-18 21:50         ` Andy Polyakov
2009-08-04  4:48       ` George Spelvin
2009-08-04  6:30         ` Linus Torvalds
2009-08-04  8:01           ` George Spelvin
2009-08-04 20:41             ` Junio C Hamano
2009-08-05 18:17               ` George Spelvin
2009-08-05 20:36                 ` Johannes Schindelin
2009-08-05 20:44                 ` Junio C Hamano
2009-08-05 20:55                 ` Linus Torvalds
2009-08-05 23:13                   ` Linus Torvalds
2009-08-06  1:18                     ` Linus Torvalds
2009-08-06  1:52                       ` Nicolas Pitre
2009-08-06  2:04                         ` Junio C Hamano
2009-08-06  2:10                           ` Linus Torvalds
2009-08-06  2:20                           ` Nicolas Pitre
2009-08-06  2:08                         ` Linus Torvalds
2009-08-06  3:19                           ` Artur Skawina
2009-08-06  3:31                             ` Linus Torvalds
2009-08-06  3:48                               ` Linus Torvalds [this message]
2009-08-06  4:01                                 ` Linus Torvalds
2009-08-06  4:28                                   ` Artur Skawina
2009-08-06  4:50                                     ` Linus Torvalds
2009-08-06  5:19                                       ` Artur Skawina
2009-08-06  7:03                                         ` George Spelvin
2009-08-06  4:52                                 ` George Spelvin
2009-08-06  4:08                               ` Artur Skawina
2009-08-06  4:27                                 ` Linus Torvalds
2009-08-06  5:44                                   ` Artur Skawina
2009-08-06  5:56                                     ` Artur Skawina
2009-08-06  7:45                                       ` Artur Skawina
2009-08-06 18:49                       ` Erik Faye-Lund
2009-08-04  6:40         ` Linus Torvalds
2009-08-18 21:26     ` Andy Polyakov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=alpine.LFD.2.01.0908052043082.3390@localhost.localdomain \
    --to=torvalds@linux-foundation.org \
    --cc=art.08.09@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=linux@horizon.com \
    --cc=nico@cam.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).