===================================================================
@@ -17,7 +17,7 @@ obj-$(CONFIG_HAS_IOMEM) += devres.o
obj-$(CONFIG_PPC64) += copypage_64.o copyuser_64.o \
memcpy_64.o usercopy_64.o mem_64.o string.o \
checksum_wrappers_64.o hweight_64.o \
- copyuser_power7.o
+ copyuser_power7.o string_64.o
obj-$(CONFIG_XMON) += sstep.o ldstfp.o
obj-$(CONFIG_KPROBES) += sstep.o ldstfp.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += sstep.o ldstfp.o
===================================================================
@@ -0,0 +1,141 @@
+/*
+ * 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, 2012
+ *
+ * Author: Anton Blanchard <anton@au.ibm.com>
+ */
+
+#include <asm/ppc_asm.h>
+
+/**
+ * __clear_user: - Zero a block of memory in user space, with less checking.
+ * @to: Destination address, in user space.
+ * @n: Number of bytes to zero.
+ *
+ * Zero a block of memory in user space. Caller must check
+ * the specified block with access_ok() before calling this function.
+ *
+ * Returns number of bytes that could not be cleared.
+ * On success, this will be zero.
+ */
+
+ .macro err1
+100:
+ .section __ex_table,"a"
+ .align 3
+ .llong 100b,.Ldo_err1
+ .previous
+ .endm
+
+ .macro err2
+200:
+ .section __ex_table,"a"
+ .align 3
+ .llong 200b,.Ldo_err2
+ .previous
+ .endm
+
+ .macro err3
+300:
+ .section __ex_table,"a"
+ .align 3
+ .llong 300b,.Ldo_err3
+ .previous
+ .endm
+
+.Ldo_err1:
+ mr r3,r8
+
+.Ldo_err2:
+ mtctr r4
+1:
+err3; stb r0,0(r3)
+ addi r3,r3,1
+ addi r4,r4,-1
+ bdnz 1b
+
+.Ldo_err3:
+ mr r3,r4
+ blr
+
+_GLOBAL(__clear_user)
+ cmpdi r4,32
+ neg r6,r3
+ li r0,0
+ blt .Lshort_clear
+ mr r8,r3
+ mtocrf 0x01,r6
+ clrldi r6,r6,(64-3)
+
+ /* Get the destination 8 byte aligned */
+ bf cr7*4+3,1f
+err1; stb r0,0(r3)
+ addi r3,r3,1
+
+1: bf cr7*4+2,2f
+err1; sth r0,0(r3)
+ addi r3,r3,2
+
+2: bf cr7*4+1,3f
+err1; stw r0,0(r3)
+ addi r3,r3,4
+
+3: sub r4,r4,r6
+ srdi r6,r4,5
+ cmpdi r4,32
+ blt .Lshort_clear
+ mtctr r6
+
+ /* Do 32 byte chunks */
+4:
+err2; std r0,0(r3)
+err2; std r0,8(r3)
+err2; std r0,16(r3)
+err2; std r0,24(r3)
+ addi r3,r3,32
+ addi r4,r4,-32
+ bdnz 4b
+
+.Lshort_clear:
+ /* up to 31 bytes to go */
+ cmpdi r4,16
+ blt 6f
+err2; std r0,0(r3)
+err2; std r0,8(r3)
+ addi r3,r3,16
+ addi r4,r4,-16
+
+ /* Up to 15 bytes to go */
+6: mr r8,r3
+ clrldi r4,r4,(64-4)
+ mtocrf 0x01,r4
+ bf cr7*4+0,7f
+err1; std r0,0(r3)
+ addi r3,r3,8
+
+7: bf cr7*4+1,8f
+err1; stw r0,0(r3)
+ addi r3,r3,4
+
+8: bf cr7*4+2,9f
+err1; sth r0,0(r3)
+ addi r3,r3,2
+
+9: bf cr7*4+3,10f
+err1; stb r0,0(r3)
+
+10: li r3,0
+ blr
===================================================================
@@ -119,6 +119,7 @@ _GLOBAL(memchr)
2: li r3,0
blr
+#ifdef CONFIG_PPC32
_GLOBAL(__clear_user)
addi r6,r3,-4
li r3,0
@@ -160,6 +161,7 @@ _GLOBAL(__clear_user)
PPC_LONG 1b,91b
PPC_LONG 8b,92b
.text
+#endif
_GLOBAL(__strncpy_from_user)
addi r6,r3,-1
I noticed __clear_user high up in a profile of one of my RAID stress tests. The testcase was doing a dd from /dev/zero which ends up calling __clear_user. __clear_user is basically a loop with a single 4 byte store which is horribly slow. We can do much better by aligning the desination and doing 32 bytes of 8 byte stores in a loop. The following testcase was used to verify the patch: http://ozlabs.org/~anton/junkcode/stress_clear_user.c To show the improvement in performance I ran a dd from /dev/zero to /dev/null on a POWER7 box: Before: # dd if=/dev/zero of=/dev/null bs=1M count=10000 10485760000 bytes (10 GB) copied, 3.72379 s, 2.8 GB/s After: # time dd if=/dev/zero of=/dev/null bs=1M count=10000 10485760000 bytes (10 GB) copied, 0.728318 s, 14.4 GB/s Over 5x faster. Signed-off-by: Anton Blanchard <anton@samba.org> --- Interestingly, it picked up an issue with the old clear_user which fails when we are less than 4 bytes to the end of a page and the next page is unmapped: offset 4094 length 526 expected 2 got -1 expected 0x00 at offset 4094, got 0xff expected 0x00 at offset 4095, got 0xff We should fix that.