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>
dca230f00d