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authorHeiko Carstens <heiko.carstens@de.ibm.com>2013-11-19 14:25:17 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-11-20 09:04:55 +0100
commitdba6bb60043ed73abca8990f237db63a8cea6c50 (patch)
treecdd10045cafcd15567c00faaa66bad74164aa507 /arch/s390
parent26a35f373fbe6f21e8ad5ca4de1c01021e38fe2f (diff)
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>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/page.h38
1 files changed, 13 insertions, 25 deletions
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 316c8503a3b4..114258eeaacd 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -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)