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Commit 7e393220 authored by Christophe Leroy's avatar Christophe Leroy Committed by Scott Wood
Browse files

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: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarScott Wood <oss@buserror.net>
parent ac6082dd

arch/powerpc/include/asm/checksum.h

+56 −23
Original line number Diff line number Diff line
@@ -12,20 +12,6 @@ 
#ifdef CONFIG_GENERIC_CSUM

#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.
@@ -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

arch/powerpc/lib/checksum_32.S

+2 −2
Original line number Diff line number Diff line
@@ -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 */

arch/powerpc/lib/checksum_64.S

+2 −2
Original line number Diff line number Diff line
@@ -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? */

arch/powerpc/lib/ppc_ksyms.c

+1 −1
Original line number Diff line number Diff line
@@ -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