On Mon, Aug 13, 2012 at 02:43:34PM +0300, Kirill A. Shutemov wrote:
> $ cat test.c
> #include <stdio.h>
> #include <sys/mman.h>
>
> #define SIZE 1024*1024*1024
>
> void clear_page_nocache_sse2(void *page) __attribute__((regparm(1)));
>
> int main(int argc, char** argv)
> {
> char *p;
> unsigned long i, j;
>
> p = mmap(NULL, SIZE, PROT_WRITE|PROT_READ,
> MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
> for(j = 0; j < 100; j++) {
> for(i = 0; i < SIZE; i += 4096) {
> clear_page_nocache_sse2(p + i);
> }
> }
>
> return 0;
> }
> $ cat clear_page_nocache_unroll32.S
> .globl clear_page_nocache_sse2
> .align 4,0x90
> clear_page_nocache_sse2:
> .cfi_startproc
> mov %eax,%edx
> xorl %eax,%eax
> movl $4096/32,%ecx
> .p2align 4
> .Lloop_sse2:
> decl %ecx
> #define PUT(x) movnti %eax,x*4(%edx)
> PUT(0)
> PUT(1)
> PUT(2)
> PUT(3)
> PUT(4)
> PUT(5)
> PUT(6)
> PUT(7)
> #undef PUT
> lea 32(%edx),%edx
> jnz .Lloop_sse2
> nop
> ret
> .cfi_endproc
> .type clear_page_nocache_sse2, @function
> .size clear_page_nocache_sse2, .-clear_page_nocache_sse2
> $ cat clear_page_nocache_unroll64.S
> .globl clear_page_nocache_sse2
> .align 4,0x90
> clear_page_nocache_sse2:
> .cfi_startproc
> mov %eax,%edx
This must still be the 32-bit version becaue it segfaults here. Here's
why:
mmap above gives a ptr which, on 64-bit, is larger than 32-bit, i.e. it
looks like 0x7fffxxxxx000, i.e. starting from top of userspace.
Now, the mov above truncates that ptr and the thing segfaults.
Doing s/edx/rdx/g fixes it though.
Thanks.
--
Regards/Gruss,
Boris.
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