sparc64: Niagara-4 bzero/memset, plus use MRU stores in page copy.

This adds optimized memset/bzero/page-clear routines for Niagara-4.

We basically can do what powerpc has been able to do for a decade (via
the "dcbz" instruction), which is use cache line clearing stores for
bzero and memsets with a 'c' argument of zero.

As long as we make the cache initializing store to each 32-byte
subblock of the L2 cache line, it works.

As with other Niagara-4 optimized routines, the key is to make sure to
avoid any usage of the %asi register, as reads and writes to it cost
at least 50 cycles.

For the user clear cases, we don't use these new routines, we use the
Niagara-1 variants instead.  Those have to use %asi in an unavoidable
way.

A Niagara-4 8K page clear costs just under 600 cycles.

Add definitions of the MRU variants of the cache initializing store
ASIs.  By default, cache initializing stores install the line as Least
Recently Used.  If we know we're going to use the data immediately
(which is true for page copies and clears) we can use the Most
Recently Used variant, to decrease the likelyhood of the lines being
evicted before they get used.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/sparc/include/asm/asi.h b/arch/sparc/include/asm/asi.h
index cc0006dc5d4a..aace6f313716 100644
--- a/arch/sparc/include/asm/asi.h
+++ b/arch/sparc/include/asm/asi.h
@@ -270,9 +270,28 @@
 #define ASI_BLK_INIT_QUAD_LDD_P	0xe2 /* (NG) init-store, twin load,
 				      * primary, implicit
 				      */
+#define ASI_BLK_INIT_QUAD_LDD_S	0xe3 /* (NG) init-store, twin load,
+				      * secondary, implicit
+				      */
 #define ASI_BLK_P		0xf0 /* Primary, blk ld/st		*/
 #define ASI_BLK_S		0xf1 /* Secondary, blk ld/st		*/
+#define ASI_ST_BLKINIT_MRU_P	0xf2 /* (NG4) init-store, twin load,
+				      * Most-Recently-Used, primary,
+				      * implicit
+				      */
+#define ASI_ST_BLKINIT_MRU_S	0xf2 /* (NG4) init-store, twin load,
+				      * Most-Recently-Used, secondary,
+				      * implicit
+				      */
 #define ASI_BLK_PL		0xf8 /* Primary, blk ld/st, little	*/
 #define ASI_BLK_SL		0xf9 /* Secondary, blk ld/st, little	*/
+#define ASI_ST_BLKINIT_MRU_PL	0xfa /* (NG4) init-store, twin load,
+				      * Most-Recently-Used, primary,
+				      * implicit, little-endian
+				      */
+#define ASI_ST_BLKINIT_MRU_SL	0xfb /* (NG4) init-store, twin load,
+				      * Most-Recently-Used, secondary,
+				      * implicit, little-endian
+				      */
 
 #endif /* _SPARC_ASI_H */