powerpc: Optimise 64bit csum_partial_copy_generic and add csum_and_copy_from_user

We use the same core loop as the new csum_partial, adding in the
stores and exception handling code. To keep things simple we do all the
exception fixup in csum_and_copy_from_user. This wrapper function is
modelled on the generic checksum code and is careful to always calculate
a complete checksum even if we only copied part of the data to userspace.

To test this I forced checksumming on over loopback and ran socklib (a
simple TCP benchmark). On a POWER6 575 throughput improved by 19% with
this patch. If I forced both the sender and receiver onto the same cpu
(with the hope of shifting the benchmark from being cache bandwidth limited
to cpu limited), adding this patch improved performance by 55%

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h
index 7cdf358..9ea58c0 100644
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -52,12 +52,19 @@ extern __wsum csum_partial(const void *buff, int len, __wsum sum);
 extern __wsum csum_partial_copy_generic(const void *src, void *dst,
 					      int len, __wsum sum,
 					      int *src_err, int *dst_err);
+
+#ifdef __powerpc64__
+#define _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
+extern __wsum csum_and_copy_from_user(const void __user *src, void *dst,
+				      int len, __wsum sum, int *err_ptr);
+#else
 /*
  * the same as csum_partial, but copies from src to dst while it
  * checksums.
  */
 #define csum_partial_copy_from_user(src, dst, len, sum, errp)   \
         csum_partial_copy_generic((__force const void *)(src), (dst), (len), (sum), (errp), NULL)
+#endif
 
 #define csum_partial_copy_nocheck(src, dst, len, sum)   \
         csum_partial_copy_generic((src), (dst), (len), (sum), NULL, NULL)