17968fbbd1
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> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
164 lines
2.5 KiB
ArmAsm
164 lines
2.5 KiB
ArmAsm
/*
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* String handling functions for PowerPC.
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*
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* Copyright (C) 1996 Paul Mackerras.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <asm/processor.h>
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#include <asm/errno.h>
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#include <asm/ppc_asm.h>
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.section __ex_table,"a"
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PPC_LONG_ALIGN
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.text
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_GLOBAL(strcpy)
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addi r5,r3,-1
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addi r4,r4,-1
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1: lbzu r0,1(r4)
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cmpwi 0,r0,0
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stbu r0,1(r5)
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bne 1b
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blr
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/* This clears out any unused part of the destination buffer,
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just as the libc version does. -- paulus */
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_GLOBAL(strncpy)
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PPC_LCMPI 0,r5,0
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beqlr
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mtctr r5
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addi r6,r3,-1
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addi r4,r4,-1
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1: lbzu r0,1(r4)
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cmpwi 0,r0,0
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stbu r0,1(r6)
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bdnzf 2,1b /* dec ctr, branch if ctr != 0 && !cr0.eq */
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bnelr /* if we didn't hit a null char, we're done */
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mfctr r5
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PPC_LCMPI 0,r5,0 /* any space left in destination buffer? */
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beqlr /* we know r0 == 0 here */
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2: stbu r0,1(r6) /* clear it out if so */
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bdnz 2b
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blr
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_GLOBAL(strcat)
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addi r5,r3,-1
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addi r4,r4,-1
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1: lbzu r0,1(r5)
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cmpwi 0,r0,0
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bne 1b
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addi r5,r5,-1
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1: lbzu r0,1(r4)
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cmpwi 0,r0,0
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stbu r0,1(r5)
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bne 1b
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blr
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_GLOBAL(strcmp)
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addi r5,r3,-1
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addi r4,r4,-1
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1: lbzu r3,1(r5)
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cmpwi 1,r3,0
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lbzu r0,1(r4)
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subf. r3,r0,r3
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beqlr 1
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beq 1b
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blr
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_GLOBAL(strncmp)
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PPC_LCMPI 0,r5,0
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beq- 2f
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mtctr r5
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addi r5,r3,-1
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addi r4,r4,-1
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1: lbzu r3,1(r5)
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cmpwi 1,r3,0
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lbzu r0,1(r4)
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subf. r3,r0,r3
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beqlr 1
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bdnzt eq,1b
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blr
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2: li r3,0
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blr
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_GLOBAL(strlen)
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addi r4,r3,-1
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1: lbzu r0,1(r4)
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cmpwi 0,r0,0
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bne 1b
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subf r3,r3,r4
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blr
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_GLOBAL(memcmp)
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PPC_LCMPI 0,r5,0
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beq- 2f
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mtctr r5
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addi r6,r3,-1
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addi r4,r4,-1
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1: lbzu r3,1(r6)
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lbzu r0,1(r4)
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subf. r3,r0,r3
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bdnzt 2,1b
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blr
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2: li r3,0
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blr
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_GLOBAL(memchr)
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PPC_LCMPI 0,r5,0
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beq- 2f
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mtctr r5
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addi r3,r3,-1
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1: lbzu r0,1(r3)
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cmpw 0,r0,r4
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bdnzf 2,1b
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beqlr
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2: li r3,0
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blr
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#ifdef CONFIG_PPC32
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_GLOBAL(__clear_user)
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addi r6,r3,-4
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li r3,0
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li r5,0
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cmplwi 0,r4,4
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blt 7f
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/* clear a single word */
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11: stwu r5,4(r6)
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beqlr
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/* clear word sized chunks */
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andi. r0,r6,3
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add r4,r0,r4
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subf r6,r0,r6
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srwi r0,r4,2
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andi. r4,r4,3
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mtctr r0
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bdz 7f
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1: stwu r5,4(r6)
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bdnz 1b
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/* clear byte sized chunks */
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7: cmpwi 0,r4,0
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beqlr
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mtctr r4
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addi r6,r6,3
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8: stbu r5,1(r6)
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bdnz 8b
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blr
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90: mr r3,r4
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blr
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91: mfctr r3
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slwi r3,r3,2
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add r3,r3,r4
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blr
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92: mfctr r3
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blr
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.section __ex_table,"a"
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PPC_LONG 11b,90b
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PPC_LONG 1b,91b
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PPC_LONG 8b,92b
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.text
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#endif
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