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From: Charlie Jenkins <charlie@rivosinc.com>
To: Charlie Jenkins <charlie@rivosinc.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Conor Dooley <conor@kernel.org>,
	Samuel Holland <samuel.holland@sifive.com>,
	David Laight <David.Laight@aculab.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>,
	David Laight <david.laight@aculab.com>
Subject: [PATCH v7 1/4] asm-generic: Improve csum_fold
Date: Tue, 19 Sep 2023 11:44:30 -0700	[thread overview]
Message-ID: <20230919-optimize_checksum-v7-1-06c7d0ddd5d6@rivosinc.com> (raw)
In-Reply-To: <20230919-optimize_checksum-v7-0-06c7d0ddd5d6@rivosinc.com>

This csum_fold implementation introduced into arch/arc by Vineet Gupta
is better than the default implementation on at least arc, x86, and
riscv. Using GCC trunk and compiling non-inlined version, this
implementation has 41.6667%, 25% fewer instructions on riscv64, x86-64
respectively with -O3 optimization. Most implmentations override this
default in asm, but this should be more performant than all of those
other implementations except for arm which has barrel shifting and
sparc32 which has a carry flag.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: David Laight <david.laight@aculab.com>
---
 include/asm-generic/checksum.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/checksum.h b/include/asm-generic/checksum.h
index 43e18db89c14..ad928cce268b 100644
--- a/include/asm-generic/checksum.h
+++ b/include/asm-generic/checksum.h
@@ -2,6 +2,8 @@
 #ifndef __ASM_GENERIC_CHECKSUM_H
 #define __ASM_GENERIC_CHECKSUM_H
 
+#include <linux/bitops.h>
+
 /*
  * computes the checksum of a memory block at buff, length len,
  * and adds in "sum" (32-bit)
@@ -31,9 +33,7 @@ extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
 static inline __sum16 csum_fold(__wsum csum)
 {
 	u32 sum = (__force u32)csum;
-	sum = (sum & 0xffff) + (sum >> 16);
-	sum = (sum & 0xffff) + (sum >> 16);
-	return (__force __sum16)~sum;
+	return (__force __sum16)((~sum - ror32(sum, 16)) >> 16);
 }
 #endif
 

-- 
2.42.0


WARNING: multiple messages have this Message-ID (diff)
From: Charlie Jenkins <charlie@rivosinc.com>
To: Charlie Jenkins <charlie@rivosinc.com>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Conor Dooley <conor@kernel.org>,
	 Samuel Holland <samuel.holland@sifive.com>,
	 David Laight <David.Laight@aculab.com>,
	linux-riscv@lists.infradead.org,  linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	 Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>,
	 David Laight <david.laight@aculab.com>
Subject: [PATCH v7 1/4] asm-generic: Improve csum_fold
Date: Tue, 19 Sep 2023 11:44:30 -0700	[thread overview]
Message-ID: <20230919-optimize_checksum-v7-1-06c7d0ddd5d6@rivosinc.com> (raw)
In-Reply-To: <20230919-optimize_checksum-v7-0-06c7d0ddd5d6@rivosinc.com>

This csum_fold implementation introduced into arch/arc by Vineet Gupta
is better than the default implementation on at least arc, x86, and
riscv. Using GCC trunk and compiling non-inlined version, this
implementation has 41.6667%, 25% fewer instructions on riscv64, x86-64
respectively with -O3 optimization. Most implmentations override this
default in asm, but this should be more performant than all of those
other implementations except for arm which has barrel shifting and
sparc32 which has a carry flag.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: David Laight <david.laight@aculab.com>
---
 include/asm-generic/checksum.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/checksum.h b/include/asm-generic/checksum.h
index 43e18db89c14..ad928cce268b 100644
--- a/include/asm-generic/checksum.h
+++ b/include/asm-generic/checksum.h
@@ -2,6 +2,8 @@
 #ifndef __ASM_GENERIC_CHECKSUM_H
 #define __ASM_GENERIC_CHECKSUM_H
 
+#include <linux/bitops.h>
+
 /*
  * computes the checksum of a memory block at buff, length len,
  * and adds in "sum" (32-bit)
@@ -31,9 +33,7 @@ extern __sum16 ip_fast_csum(const void *iph, unsigned int ihl);
 static inline __sum16 csum_fold(__wsum csum)
 {
 	u32 sum = (__force u32)csum;
-	sum = (sum & 0xffff) + (sum >> 16);
-	sum = (sum & 0xffff) + (sum >> 16);
-	return (__force __sum16)~sum;
+	return (__force __sum16)((~sum - ror32(sum, 16)) >> 16);
 }
 #endif
 

-- 
2.42.0


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  reply	other threads:[~2023-09-19 18:45 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-19 18:44 [PATCH v7 0/4] riscv: Add fine-tuned checksum functions Charlie Jenkins
2023-09-19 18:44 ` Charlie Jenkins
2023-09-19 18:44 ` Charlie Jenkins [this message]
2023-09-19 18:44   ` [PATCH v7 1/4] asm-generic: Improve csum_fold Charlie Jenkins
2023-09-19 18:44 ` [PATCH v7 2/4] riscv: Checksum header Charlie Jenkins
2023-09-19 18:44   ` Charlie Jenkins
2023-10-12 14:54   ` Conor Dooley
2023-10-12 14:54     ` Conor Dooley
2023-10-25  6:50   ` Wang, Xiao W
2023-10-25  6:50     ` Wang, Xiao W
2023-10-25 20:37     ` Charlie Jenkins
2023-10-25 20:37       ` Charlie Jenkins
2023-10-25 20:52       ` Arnd Bergmann
2023-10-25 20:52         ` Arnd Bergmann
2023-10-25 21:11         ` Charlie Jenkins
2023-10-25 21:11           ` Charlie Jenkins
2023-10-25 21:18           ` Arnd Bergmann
2023-10-25 21:18             ` Arnd Bergmann
2023-10-25 21:20             ` Charlie Jenkins
2023-10-25 21:20               ` Charlie Jenkins
2023-09-19 18:44 ` [PATCH v7 3/4] riscv: Add checksum library Charlie Jenkins
2023-09-19 18:44   ` Charlie Jenkins
2023-10-12 14:51   ` Conor Dooley
2023-10-12 14:51     ` Conor Dooley
2023-10-25  7:29   ` Wang, Xiao W
2023-10-25  7:29     ` Wang, Xiao W
2023-09-19 18:44 ` [PATCH v7 4/4] riscv: Test checksum functions Charlie Jenkins
2023-09-19 18:44   ` Charlie Jenkins

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