Currently kernel believes that all ARM CPUs have L1_CACHE_SHIFT == 5.
It's not true at least for CPUs based on Cortex-A8.
List of CPUs with cache line size != 32 should be expanded later.
V2:
- remove unnecessary parens
Signed-off-by: Kirill A. Shutemov <[email protected]>
---
arch/arm/include/asm/cache.h | 2 +-
arch/arm/mm/Kconfig | 5 +++++
2 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/arch/arm/include/asm/cache.h b/arch/arm/include/asm/cache.h
index feaa75f..66c160b 100644
--- a/arch/arm/include/asm/cache.h
+++ b/arch/arm/include/asm/cache.h
@@ -4,7 +4,7 @@
#ifndef __ASMARM_CACHE_H
#define __ASMARM_CACHE_H
-#define L1_CACHE_SHIFT 5
+#define L1_CACHE_SHIFT CONFIG_ARM_L1_CACHE_SHIFT
#define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
/*
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 83c025e..3c37d4c 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -771,3 +771,8 @@ config CACHE_XSC3L2
select OUTER_CACHE
help
This option enables the L2 cache on XScale3.
+
+config ARM_L1_CACHE_SHIFT
+ int
+ default 6 if ARCH_OMAP3
+ default 5
--
1.6.4.2
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.
V3:
- fix typo
V2:
- include <asm/cache.h>
- remove unnecessary parens and fix style
Signed-off-by: Siarhei Siamashka <[email protected]>
Signed-off-by: Kirill A. Shutemov <[email protected]>
---
arch/arm/lib/copy_page.S | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/arm/lib/copy_page.S b/arch/arm/lib/copy_page.S
index 6ae04db..6ee2f67 100644
--- a/arch/arm/lib/copy_page.S
+++ b/arch/arm/lib/copy_page.S
@@ -12,8 +12,9 @@
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
+#include <asm/cache.h>
-#define COPY_COUNT (PAGE_SZ/64 PLD( -1 ))
+#define COPY_COUNT (PAGE_SZ / (2 * L1_CACHE_BYTES) PLD( -1 ))
.text
.align 5
@@ -26,17 +27,16 @@
ENTRY(copy_page)
stmfd sp!, {r4, lr} @ 2
PLD( pld [r1, #0] )
- PLD( pld [r1, #32] )
+ PLD( pld [r1, #L1_CACHE_BYTES] )
mov r2, #COPY_COUNT @ 1
ldmia r1!, {r3, r4, ip, lr} @ 4+1
-1: PLD( pld [r1, #64] )
- PLD( pld [r1, #96] )
-2: stmia r0!, {r3, r4, ip, lr} @ 4
- ldmia r1!, {r3, r4, ip, lr} @ 4+1
- stmia r0!, {r3, r4, ip, lr} @ 4
- ldmia r1!, {r3, r4, ip, lr} @ 4+1
+1: PLD( pld [r1, #2 * L1_CACHE_BYTES])
+ PLD( pld [r1, #3 * L1_CACHE_BYTES])
+2:
+ .rept (2 * L1_CACHE_BYTES / 16 - 1)
stmia r0!, {r3, r4, ip, lr} @ 4
ldmia r1!, {r3, r4, ip, lr} @ 4
+ .endr
subs r2, r2, #1 @ 1
stmia r0!, {r3, r4, ip, lr} @ 4
ldmgtia r1!, {r3, r4, ip, lr} @ 4
--
1.6.4.2
On Sat, Sep 12, 2009 at 11:48:30PM +0300, Kirill A. Shutemov wrote:
> Currently kernel believes that all ARM CPUs have L1_CACHE_SHIFT == 5.
> It's not true at least for CPUs based on Cortex-A8.
Please send this to the patch system. There's no need to add the "V2"
comments to it when you do.
On Mon, Sep 21, 2009 at 11:37 AM, Russell King - ARM Linux
<[email protected]> wrote:
> On Sat, Sep 12, 2009 at 11:48:30PM +0300, Kirill A. Shutemov wrote:
>> Currently kernel believes that all ARM CPUs have L1_CACHE_SHIFT == 5.
>> It's not true at least for CPUs based on Cortex-A8.
>
> Please send this to the patch system. There's no need to add the "V2"
> comments to it when you do.
>
#5716, #5717
BTW, I ,my pathes without change log in your git tree. Commits 910a17e
and dca230f. What is wrong with it?
On Mon, Sep 21, 2009 at 02:19:57PM +0300, Kirill A. Shutemov wrote:
> On Mon, Sep 21, 2009 at 11:37 AM, Russell King - ARM Linux
> <[email protected]> wrote:
> > On Sat, Sep 12, 2009 at 11:48:30PM +0300, Kirill A. Shutemov wrote:
> >> Currently kernel believes that all ARM CPUs have L1_CACHE_SHIFT == 5.
> >> It's not true at least for CPUs based on Cortex-A8.
> >
> > Please send this to the patch system. ?There's no need to add the "V2"
> > comments to it when you do.
> >
>
> #5716, #5717
>
> BTW, I ,my pathes without change log in your git tree. Commits 910a17e
> and dca230f. What is wrong with it?
No need to resend them - sorry, I'd forgotten I'd merged them.