forked from Minki/linux
dca230f00d
Optimized version of copy_page() was written with assumption that cache
line size is 32 bytes. On Cortex-A8 cache line size is 64 bytes.
This patch tries to generalize copy_page() to work with any cache line
size if cache line size is multiple of 16 and page size is multiple of
two cache line size.
After this optimization we've got ~25% speedup on OMAP3(tested in
userspace).
There is test for kernelspace which trigger copy-on-write after fork():
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define BUF_SIZE (10000*4096)
#define NFORK 200
int main(int argc, char **argv)
{
char *buf = malloc(BUF_SIZE);
int i;
memset(buf, 0, BUF_SIZE);
for(i = 0; i < NFORK; i++) {
if (fork()) {
wait(NULL);
} else {
int j;
for(j = 0; j < BUF_SIZE; j+= 4096)
buf[j] = (j & 0xFF) + 1;
break;
}
}
free(buf);
return 0;
}
Before optimization this test takes ~66 seconds, after optimization
takes ~56 seconds.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@nokia.com>
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
48 lines
1.3 KiB
ArmAsm
48 lines
1.3 KiB
ArmAsm
/*
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* linux/arch/arm/lib/copypage.S
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*
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* Copyright (C) 1995-1999 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* ASM optimised string functions
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/asm-offsets.h>
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#include <asm/cache.h>
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#define COPY_COUNT (PAGE_SZ / (2 * L1_CACHE_BYTES) PLD( -1 ))
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.text
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.align 5
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/*
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* StrongARM optimised copy_page routine
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* now 1.78bytes/cycle, was 1.60 bytes/cycle (50MHz bus -> 89MB/s)
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* Note that we probably achieve closer to the 100MB/s target with
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* the core clock switching.
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*/
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ENTRY(copy_page)
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stmfd sp!, {r4, lr} @ 2
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PLD( pld [r1, #0] )
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PLD( pld [r1, #L1_CACHE_BYTES] )
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mov r2, #COPY_COUNT @ 1
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ldmia r1!, {r3, r4, ip, lr} @ 4+1
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1: PLD( pld [r1, #2 * L1_CACHE_BYTES])
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PLD( pld [r1, #3 * L1_CACHE_BYTES])
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2:
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.rept (2 * L1_CACHE_BYTES / 16 - 1)
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stmia r0!, {r3, r4, ip, lr} @ 4
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ldmia r1!, {r3, r4, ip, lr} @ 4
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.endr
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subs r2, r2, #1 @ 1
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stmia r0!, {r3, r4, ip, lr} @ 4
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ldmgtia r1!, {r3, r4, ip, lr} @ 4
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bgt 1b @ 1
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PLD( ldmeqia r1!, {r3, r4, ip, lr} )
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PLD( beq 2b )
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ldmfd sp!, {r4, pc} @ 3
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ENDPROC(copy_page)
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