lib: Introduce some memory copy macros and functions

The kernel's memcpy and memmove is very inefficient. But the glibc version is
quite fast, in some cases it is 10 times faster than the kernel version. So I
introduce some memory copy macros and functions of the glibc to improve the
kernel version's performance.

The strategy of the memory functions is:
1. Copy bytes until the destination pointer is aligned.
2. Copy words in unrolled loops. If the source and destination are not aligned
   in the same way, use word memory operations, but shift and merge two read
   words before writing.
3. Copy the few remaining bytes.

Signed-off-by: Miao Xie <[email protected]>

Conflicts:

	lib/Makefile

include/linux/memcopy.h

@@ -0,0 +1,226 @@
+/*
+ * memcopy.h -- definitions for memory copy functions.  Generic C version.
+ *
+ * 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.,
+ * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * The code is derived from the GNU C Library.
+ * Copyright (C) 1991, 1992, 1993, 1997, 2004 Free Software Foundation, Inc.
+ */
+#ifndef _LINUX_MEMCOPY_H_
+#define _LINUX_MEMCOPY_H_
+
+/*
+ * The strategy of the memory functions is:
+ *
+ *   1. Copy bytes until the destination pointer is aligned.
+ *
+ *   2. Copy words in unrolled loops.  If the source and destination
+ *      are not aligned in the same way, use word memory operations,
+ *      but shift and merge two read words before writing.
+ *
+ *   3. Copy the few remaining bytes.
+ *
+ * This is fast on processors that have at least 10 registers for
+ * allocation by GCC, and that can access memory at reg+const in one
+ * instruction.
+ */
+
+#include <linux/types.h>
+#include <linux/compiler.h>
+#include <asm/byteorder.h>
+
+/*
+ * The macros defined in this file are:
+ *
+ * BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
+ * 
+ * BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
+ * 
+ * WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
+ * 
+ * WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
+ * 
+ * MERGE(old_word, sh_1, new_word, sh_2)
+ * 
+ * MEM_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
+ * 
+ * MEM_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
+ */
+
+#define OP_T_THRESHOLD	16
+
+/*
+ * Type to use for aligned memory operations.
+ * This should normally be the biggest type supported by a single load
+ * and store.
+ */
+#define	op_t	unsigned long int
+#define OPSIZ	(sizeof(op_t))
+
+/* Type to use for unaligned operations.  */
+typedef unsigned char byte;
+
+#ifndef MERGE
+# ifdef __LITTLE_ENDIAN
+#  define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
+# elif defined(__BIG_ENDIAN)
+#  define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
+# else
+#  error "Macro MERGE() hasn't defined!"
+# endif
+#endif
+
+/*
+ * Copy exactly NBYTES bytes from SRC_BP to DST_BP,
+ * without any assumptions about alignment of the pointers.
+ */
+#ifndef BYTE_COPY_FWD
+#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes)				      \
+do {									      \
+	size_t __nbytes = (nbytes);					      \
+	while (__nbytes > 0) {						      \
+		byte __x = ((byte *) src_bp)[0];			      \
+		src_bp += 1;						      \
+		__nbytes -= 1;						      \
+		((byte *) dst_bp)[0] = __x;				      \
+		dst_bp += 1;						      \
+	}								      \
+} while (0)
+#endif
+
+/*
+ * Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
+ * beginning at the bytes right before the pointers and continuing towards
+ * smaller addresses.  Don't assume anything about alignment of the
+ * pointers.
+ */
+#ifndef BYTE_COPY_BWD
+#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes)				      \
+do {									      \
+	size_t __nbytes = (nbytes);					      \
+	while (__nbytes > 0) {						      \
+		byte __x;						      \
+		src_ep -= 1;						      \
+		__x = ((byte *) src_ep)[0];				      \
+		dst_ep -= 1;						      \
+		__nbytes -= 1;						      \
+		((byte *) dst_ep)[0] = __x;				      \
+	}								      \
+} while (0)
+#endif
+/*
+ * Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with
+ * the assumption that DST_BP is aligned on an OPSIZ multiple.  If
+ * not all bytes could be easily copied, store remaining number of bytes
+ * in NBYTES_LEFT, otherwise store 0.
+ */
+extern void _wordcopy_fwd_aligned(long int, long int, size_t);
+extern void _wordcopy_fwd_dest_aligned(long int, long int, size_t);
+#ifndef WORD_COPY_FWD
+#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes)		      \
+do {									      \
+	if (src_bp % OPSIZ == 0)					      \
+		_wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);     \
+	else								      \
+		_wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);\
+									      \
+	src_bp += (nbytes) & -OPSIZ;					      \
+	dst_bp += (nbytes) & -OPSIZ;					      \
+	(nbytes_left) = (nbytes) % OPSIZ;				      \
+} while (0)
+#endif
+
+/*
+ * Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
+ * beginning at the words (of type op_t) right before the pointers and
+ * continuing towards smaller addresses.  May take advantage of that
+ * DST_END_PTR is aligned on an OPSIZ multiple.  If not all bytes could be
+ * easily copied, store remaining number of bytes in NBYTES_REMAINING,
+ * otherwise store 0.
+ */
+extern void _wordcopy_bwd_aligned(long int, long int, size_t);
+extern void _wordcopy_bwd_dest_aligned(long int, long int, size_t);
+#ifndef WORD_COPY_BWD
+#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes)		      \
+do {									      \
+	if (src_ep % OPSIZ == 0)					      \
+		_wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);     \
+	else								      \
+		_wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);\
+									      \
+	src_ep -= (nbytes) & -OPSIZ;					      \
+	dst_ep -= (nbytes) & -OPSIZ;					      \
+	(nbytes_left) = (nbytes) % OPSIZ;				      \
+} while (0)
+#endif
+
+/* Copy memory from the beginning to the end */
+#ifndef MEM_COPY_FWD
+static __always_inline void mem_copy_fwd(unsigned long dstp,
+					unsigned long srcp,
+					size_t count)
+{
+	/* If there not too few bytes to copy, use word copy. */
+	if (count >= OP_T_THRESHOLD) {
+		/* Copy just a few bytes to make dstp aligned. */
+		count -= (-dstp) % OPSIZ;
+		BYTE_COPY_FWD(dstp, srcp, (-dstp) % OPSIZ);
+
+		/*
+		 * Copy from srcp to dstp taking advantage of the known
+		 * alignment of dstp. Number if bytes remaining is put in
+		 * the third argument.
+		 */
+		WORD_COPY_FWD(dstp, srcp, count, count);
+
+		/* Fall out and copy the tail. */
+	}
+
+	/* There are just a few bytes to copy. Use byte memory operations. */
+	BYTE_COPY_FWD(dstp, srcp, count);
+}
+#endif
+
+/* Copy memory from the end to the beginning.  */
+#ifndef MEM_COPY_BWD
+static __always_inline void mem_copy_bwd(unsigned long dstp,
+					unsigned long srcp,
+					size_t count)
+{
+	srcp += count;
+	dstp += count;
+
+	/* If there not too few bytes to copy, use word copy. */
+	if (count >= OP_T_THRESHOLD) {
+		/* Copy just a few bytes to make dstp aligned. */
+		count -= dstp % OPSIZ;
+		BYTE_COPY_BWD(dstp, srcp, dstp % OPSIZ);
+
+		/*
+		 * Copy from srcp to dstp taking advantage of the known
+		 * alignment of dstp. Number if bytes remaining is put in
+		 * the third argument.
+		 */
+		WORD_COPY_BWD(dstp, srcp, count, count);
+
+		/* Fall out and copy the tail. */
+	}
+
+	/* There are just a few bytes to copy. Use byte memory operations. */
+	BYTE_COPY_BWD (dstp, srcp, count);
+}
+#endif
+
+#endif

lib/Makefile

@@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
 	 proportions.o prio_heap.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o \
-	 memory_alloc.o
+	 memory_alloc.o memcopy.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o