powerpc: New copy_4K_page()

This new copy_4K_page() function was originally tuned for the best
performance on the Cell processor, but after testing on more 64bit
powerpc chips it was found that with a small modification it either
matched the performance offered by the current mainline version or
bettered it by a small amount.

It was found that on a Cell-based QS22 blade the amount of system
time measured when compiling a 2.6.26 pseries_defconfig decreased
by 4%. Using the same test, a 4-way 970MP machine saw a decrease of
2% in system time. No noticeable change was seen on Power4, Power5
or Power6.

The 4096 byte page is copied in thirty-two 128 byte strides. An
initial setup loop executes dcbt instructions for the whole source
page and dcbz instructions for the whole destination page. To do
this, the cache line size is retrieved from ppc64_caches.

A new CPU feature bit, CPU_FTR_CP_USE_DCBTZ, (introduced in the
previous patch) is used to make the modification to this new copy
routine - on Power4, 970 and Cell the feature bit is set so the
setup loop is executed, but on all other 64bit chips the setup
loop is nop'ed out.

Signed-off-by: Mark Nelson <markn@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/lib/copypage_64.S b/arch/powerpc/lib/copypage_64.S
index f9837f4..75f3267 100644 (file)
--- a/arch/powerpc/lib/copypage_64.S
+++ b/arch/powerpc/lib/copypage_64.S
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2002 Paul Mackerras, IBM Corp.
+ * Copyright (C) 2008 Mark Nelson, IBM Corp.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -8,112 +8,100 @@
  */
 #include <asm/processor.h>
 #include <asm/ppc_asm.h>
+#include <asm/asm-offsets.h>
+
+        .section        ".toc","aw"
+PPC64_CACHES:
+        .tc             ppc64_caches[TC],ppc64_caches
+        .section        ".text"
+
 
 _GLOBAL(copy_4K_page)
-       std     r31,-8(1)
-       std     r30,-16(1)
-       std     r29,-24(1)
-       std     r28,-32(1)
-       std     r27,-40(1)
-       std     r26,-48(1)
-       std     r25,-56(1)
-       std     r24,-64(1)
-       std     r23,-72(1)
-       std     r22,-80(1)
-       std     r21,-88(1)
-       std     r20,-96(1)
-       li      r5,4096/32 - 1
+       li      r5,4096         /* 4K page size */
+BEGIN_FTR_SECTION
+       ld      r10,PPC64_CACHES@toc(r2)
+       lwz     r11,DCACHEL1LOGLINESIZE(r10)    /* log2 of cache line size */
+       lwz     r12,DCACHEL1LINESIZE(r10)       /* get cache line size */
+       li      r9,0
+       srd     r8,r5,r11
+
+       mtctr   r8
+setup:
+       dcbt    r9,r4
+       dcbz    r9,r3
+       add     r9,r9,r12
+       bdnz    setup
+END_FTR_SECTION_IFSET(CPU_FTR_CP_USE_DCBTZ)
        addi    r3,r3,-8
-       li      r12,5
-0:     addi    r5,r5,-24
-       mtctr   r12
-       ld      r22,640(4)
-       ld      r21,512(4)
-       ld      r20,384(4)
-       ld      r11,256(4)
-       ld      r9,128(4)
-       ld      r7,0(4)
-       ld      r25,648(4)
-       ld      r24,520(4)
-       ld      r23,392(4)
-       ld      r10,264(4)
-       ld      r8,136(4)
-       ldu     r6,8(4)
-       cmpwi   r5,24
-1:     std     r22,648(3)
-       std     r21,520(3)
-       std     r20,392(3)
-       std     r11,264(3)
-       std     r9,136(3)
-       std     r7,8(3)
-       ld      r28,648(4)
-       ld      r27,520(4)
-       ld      r26,392(4)
-       ld      r31,264(4)
-       ld      r30,136(4)
-       ld      r29,8(4)
-       std     r25,656(3)
-       std     r24,528(3)
-       std     r23,400(3)
-       std     r10,272(3)
-       std     r8,144(3)
-       std     r6,16(3)
-       ld      r22,656(4)
-       ld      r21,528(4)
-       ld      r20,400(4)
-       ld      r11,272(4)
-       ld      r9,144(4)
-       ld      r7,16(4)
-       std     r28,664(3)
-       std     r27,536(3)
-       std     r26,408(3)
-       std     r31,280(3)
-       std     r30,152(3)
-       stdu    r29,24(3)
-       ld      r25,664(4)
-       ld      r24,536(4)
-       ld      r23,408(4)
-       ld      r10,280(4)
-       ld      r8,152(4)
-       ldu     r6,24(4)
+       srdi    r8,r5,7         /* page is copied in 128 byte strides */
+       addi    r8,r8,-1        /* one stride copied outside loop */
+
+       mtctr   r8
+
+       ld      r5,0(r4)
+       ld      r6,8(r4)
+       ld      r7,16(r4)
+       ldu     r8,24(r4)
+1:     std     r5,8(r3)
+       ld      r9,8(r4)
+       std     r6,16(r3)
+       ld      r10,16(r4)
+       std     r7,24(r3)
+       ld      r11,24(r4)
+       std     r8,32(r3)
+       ld      r12,32(r4)
+       std     r9,40(r3)
+       ld      r5,40(r4)
+       std     r10,48(r3)
+       ld      r6,48(r4)
+       std     r11,56(r3)
+       ld      r7,56(r4)
+       std     r12,64(r3)
+       ld      r8,64(r4)
+       std     r5,72(r3)
+       ld      r9,72(r4)
+       std     r6,80(r3)
+       ld      r10,80(r4)
+       std     r7,88(r3)
+       ld      r11,88(r4)
+       std     r8,96(r3)
+       ld      r12,96(r4)
+       std     r9,104(r3)
+       ld      r5,104(r4)
+       std     r10,112(r3)
+       ld      r6,112(r4)
+       std     r11,120(r3)
+       ld      r7,120(r4)
+       stdu    r12,128(r3)
+       ldu     r8,128(r4)
        bdnz    1b
-       std     r22,648(3)
-       std     r21,520(3)
-       std     r20,392(3)
-       std     r11,264(3)
-       std     r9,136(3)
-       std     r7,8(3)
-       addi    r4,r4,640
-       addi    r3,r3,648
-       bge     0b
-       mtctr   r5
-       ld      r7,0(4)
-       ld      r8,8(4)
-       ldu     r9,16(4)
-3:     ld      r10,8(4)
-       std     r7,8(3)
-       ld      r7,16(4)
-       std     r8,16(3)
-       ld      r8,24(4)
-       std     r9,24(3)
-       ldu     r9,32(4)
-       stdu    r10,32(3)
-       bdnz    3b
-4:     ld      r10,8(4)
-       std     r7,8(3)
-       std     r8,16(3)
-       std     r9,24(3)
-       std     r10,32(3)
-9:     ld      r20,-96(1)
-       ld      r21,-88(1)
-       ld      r22,-80(1)
-       ld      r23,-72(1)
-       ld      r24,-64(1)
-       ld      r25,-56(1)
-       ld      r26,-48(1)
-       ld      r27,-40(1)
-       ld      r28,-32(1)
-       ld      r29,-24(1)
-       ld      r30,-16(1)
-       ld      r31,-8(1)
+
+       std     r5,8(r3)
+       ld      r9,8(r4)
+       std     r6,16(r3)
+       ld      r10,16(r4)
+       std     r7,24(r3)
+       ld      r11,24(r4)
+       std     r8,32(r3)
+       ld      r12,32(r4)
+       std     r9,40(r3)
+       ld      r5,40(r4)
+       std     r10,48(r3)
+       ld      r6,48(r4)
+       std     r11,56(r3)
+       ld      r7,56(r4)
+       std     r12,64(r3)
+       ld      r8,64(r4)
+       std     r5,72(r3)
+       ld      r9,72(r4)
+       std     r6,80(r3)
+       ld      r10,80(r4)
+       std     r7,88(r3)
+       ld      r11,88(r4)
+       std     r8,96(r3)
+       ld      r12,96(r4)
+       std     r9,104(r3)
+       std     r10,112(r3)
+       std     r11,120(r3)
+       std     r12,128(r3)
        blr