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s390/mm: optimize copy_page

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Always use the mvcl instruction to copy a page instead of mvpg or a
couple of mvc instructions.
Copying a huge page is 25% faster this way. Also bypass caches when
copying pages since only parts of a page will be used afterwards.
Especially when copying a huge page this would kick everything out
of the L1 and L2 data caches on a zEC12 machine.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Heiko Carstens 2013-11-19 14:25:17 +01:00 committed by Martin Schwidefsky
parent 26a35f373f
commit dba6bb6004
1 changed files with 13 additions and 25 deletions
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38
arch/s390/include/asm/page.h
View file

@ -48,33 +48,21 @@ static inline void clear_page(void *page)
: "memory", "cc");
}
/*
* copy_page uses the mvcl instruction with 0xb0 padding byte in order to
* bypass caches when copying a page. Especially when copying huge pages
* this keeps L1 and L2 data caches alive.
*/
static inline void copy_page(void *to, void *from)
{
if (MACHINE_HAS_MVPG) {
register unsigned long reg0 asm ("0") = 0;
asm volatile(
" mvpg %0,%1"
: : "a" (to), "a" (from), "d" (reg0)
: "memory", "cc");
} else
asm volatile(
" mvc 0(256,%0),0(%1)\n"
" mvc 256(256,%0),256(%1)\n"
" mvc 512(256,%0),512(%1)\n"
" mvc 768(256,%0),768(%1)\n"
" mvc 1024(256,%0),1024(%1)\n"
" mvc 1280(256,%0),1280(%1)\n"
" mvc 1536(256,%0),1536(%1)\n"
" mvc 1792(256,%0),1792(%1)\n"
" mvc 2048(256,%0),2048(%1)\n"
" mvc 2304(256,%0),2304(%1)\n"
" mvc 2560(256,%0),2560(%1)\n"
" mvc 2816(256,%0),2816(%1)\n"
" mvc 3072(256,%0),3072(%1)\n"
" mvc 3328(256,%0),3328(%1)\n"
" mvc 3584(256,%0),3584(%1)\n"
" mvc 3840(256,%0),3840(%1)\n"
: : "a" (to), "a" (from) : "memory");
register void *reg2 asm ("2") = to;
register unsigned long reg3 asm ("3") = 0x1000;
register void *reg4 asm ("4") = from;
register unsigned long reg5 asm ("5") = 0xb0001000;
asm volatile(
" mvcl 2,4"
: "+d" (reg2), "+d" (reg3), "+d" (reg4), "+d" (reg5)
: : "memory", "cc");
}
#define clear_user_page(page, vaddr, pg) clear_page(page)