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, 65 insertions, 0 deletions

diff --git a/arch/powerpc/lib/checksum_wrappers_64.c b/arch/powerpc/lib/checksum_wrappers_64.c
new file mode 100644
index 00000000000..614cff1a8e0
--- /dev/null
+++ b/arch/powerpc/lib/checksum_wrappers_64.c
@@ -0,0 +1,65 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2010
+ *
+ * Author: Anton Blanchard <anton@au.ibm.com>
+ */
+#include <linux/module.h>
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <asm/checksum.h>
+#include <asm/uaccess.h>
+
+__wsum csum_and_copy_from_user(const void __user *src, void *dst,
+			       int len, __wsum sum, int *err_ptr)
+{
+	unsigned int csum;
+
+	might_sleep();
+
+	*err_ptr = 0;
+
+	if (!len) {
+		csum = 0;
+		goto out;
+	}
+
+	if (unlikely((len < 0) || !access_ok(VERIFY_READ, src, len))) {
+		*err_ptr = -EFAULT;
+		csum = (__force unsigned int)sum;
+		goto out;
+	}
+
+	csum = csum_partial_copy_generic((void __force *)src, dst,
+					 len, sum, err_ptr, NULL);
+
+	if (unlikely(*err_ptr)) {
+		int missing = __copy_from_user(dst, src, len);
+
+		if (missing) {
+			memset(dst + len - missing, 0, missing);
+			*err_ptr = -EFAULT;
+		} else {
+			*err_ptr = 0;
+		}
+
+		csum = csum_partial(dst, len, sum);
+	}
+
+out:
+	return (__force __wsum)csum;
+}
+EXPORT_SYMBOL(csum_and_copy_from_user);