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Message-Id: <20160307174437.56E801A236B@localhost.localdomain>
Date: Mon, 7 Mar 2016 18:44:37 +0100 (CET)
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Scott Wood <oss@...error.net>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2] powerpc: optimise csum_partial() call when len is constant
csum_partial is often called for small fixed length packets
for which it is suboptimal to use the generic csum_partial()
function.
For instance, in my configuration, I got:
* One place calling it with constant len 4
* Seven places calling it with constant len 8
* Three places calling it with constant len 14
* One place calling it with constant len 20
* One place calling it with constant len 24
* One place calling it with constant len 32
This patch renames csum_partial() to __csum_partial() and
implements csum_partial() as a wrapper inline function which
* uses csum_add() for small 16bits multiple constant length
* uses ip_fast_csum() for other 32bits multiple constant
* uses __csum_partial() in all other cases
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
v2: Taken into account Scott's comments
applies on top of scottwood/linux next
arch/powerpc/include/asm/checksum.h | 79 ++++++++++++++++++++++++++-----------
arch/powerpc/lib/checksum_32.S | 4 +-
arch/powerpc/lib/checksum_64.S | 4 +-
arch/powerpc/lib/ppc_ksyms.c | 2 +-
4 files changed, 61 insertions(+), 28 deletions(-)
diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index 74cd8d8..ee655ed 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -13,20 +13,6 @@
#include <asm-generic/checksum.h>
#else
/*
- * computes the checksum of a memory block at buff, length len,
- * and adds in "sum" (32-bit)
- *
- * returns a 32-bit number suitable for feeding into itself
- * or csum_tcpudp_magic
- *
- * this function must be called with even lengths, except
- * for the last fragment, which may be odd
- *
- * it's best to have buff aligned on a 32-bit boundary
- */
-extern __wsum csum_partial(const void *buff, int len, __wsum sum);
-
-/*
* Computes the checksum of a memory block at src, length len,
* and adds in "sum" (32-bit), while copying the block to dst.
* If an access exception occurs on src or dst, it stores -EFAULT
@@ -67,15 +53,6 @@ static inline __sum16 csum_fold(__wsum sum)
return (__force __sum16)(~((__force u32)sum + tmp) >> 16);
}
-/*
- * this routine is used for miscellaneous IP-like checksums, mainly
- * in icmp.c
- */
-static inline __sum16 ip_compute_csum(const void *buff, int len)
-{
- return csum_fold(csum_partial(buff, len, 0));
-}
-
static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
unsigned short len,
unsigned short proto,
@@ -174,6 +151,62 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
return csum_fold(ip_fast_csum_nofold(iph, ihl));
}
+/*
+ * computes the checksum of a memory block at buff, length len,
+ * and adds in "sum" (32-bit)
+ *
+ * returns a 32-bit number suitable for feeding into itself
+ * or csum_tcpudp_magic
+ *
+ * this function must be called with even lengths, except
+ * for the last fragment, which may be odd
+ *
+ * it's best to have buff aligned on a 32-bit boundary
+ */
+__wsum __csum_partial(const void *buff, int len, __wsum sum);
+
+static inline __wsum csum_partial(const void *buff, int len, __wsum sum)
+{
+ if (__builtin_constant_p(len) && len <= 16 && (len & 1) == 0) {
+ if (len == 2)
+ sum = csum_add(sum, (__force __wsum)*(const u16 *)buff);
+ if (len >= 4)
+ sum = csum_add(sum, (__force __wsum)*(const u32 *)buff);
+ if (len == 6)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u16 *)(buff + 4));
+ if (len >= 8)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u32 *)(buff + 4));
+ if (len == 10)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u16 *)(buff + 8));
+ if (len >= 12)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u32 *)(buff + 8));
+ if (len == 14)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u16 *)(buff + 12));
+ if (len >= 16)
+ sum = csum_add(sum, (__force __wsum)
+ *(const u32 *)(buff + 12));
+ } else if (__builtin_constant_p(len) && (len & 3) == 0) {
+ sum = csum_add(sum, ip_fast_csum_nofold(buff, len >> 2));
+ } else {
+ sum = __csum_partial(buff, len, sum);
+ }
+ return sum;
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+static inline __sum16 ip_compute_csum(const void *buff, int len)
+{
+ return csum_fold(csum_partial(buff, len, 0));
+}
+
#endif
#endif /* __KERNEL__ */
#endif
diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
index 0d34f47..d90870a 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S
@@ -24,9 +24,9 @@
* computes the checksum of a memory block at buff, length len,
* and adds in "sum" (32-bit)
*
- * csum_partial(buff, len, sum)
+ * __csum_partial(buff, len, sum)
*/
-_GLOBAL(csum_partial)
+_GLOBAL(__csum_partial)
subi r3,r3,4
srawi. r6,r4,2 /* Divide len by 4 and also clear carry */
beq 3f /* if we're doing < 4 bytes */
diff --git a/arch/powerpc/lib/checksum_64.S b/arch/powerpc/lib/checksum_64.S
index f53f4ab..8e6e510 100644
--- a/arch/powerpc/lib/checksum_64.S
+++ b/arch/powerpc/lib/checksum_64.S
@@ -21,9 +21,9 @@
* Computes the checksum of a memory block at buff, length len,
* and adds in "sum" (32-bit).
*
- * csum_partial(r3=buff, r4=len, r5=sum)
+ * __csum_partial(r3=buff, r4=len, r5=sum)
*/
-_GLOBAL(csum_partial)
+_GLOBAL(__csum_partial)
addic r0,r5,0 /* clear carry */
srdi. r6,r4,3 /* less than 8 bytes? */
diff --git a/arch/powerpc/lib/ppc_ksyms.c b/arch/powerpc/lib/ppc_ksyms.c
index 8cd5c0b..c422812 100644
--- a/arch/powerpc/lib/ppc_ksyms.c
+++ b/arch/powerpc/lib/ppc_ksyms.c
@@ -17,7 +17,7 @@ EXPORT_SYMBOL(strcmp);
EXPORT_SYMBOL(strncmp);
#ifndef CONFIG_GENERIC_CSUM
-EXPORT_SYMBOL(csum_partial);
+EXPORT_SYMBOL(__csum_partial);
EXPORT_SYMBOL(csum_partial_copy_generic);
#endif
--
2.1.0
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