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Commit dba6bb60 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent 26a35f37

arch/s390/include/asm/page.h

+13 −25
Original line number Diff line number Diff line
@@ -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

	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(

			"	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");

		"	mvcl	2,4"

		: "+d" (reg2), "+d" (reg3), "+d" (reg4), "+d" (reg5)

		: : "memory", "cc");

}



#define clear_user_page(page, vaddr, pg)	clear_page(page)