s390/mm: optimize copy_page
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>
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 316c850..114258e 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -48,33 +48,21 @@
: "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)
