[linuxsh-dev] SH-4 cache performance improvement

[SUGIOKA T. <su...@it...>]

Hi, all.
I'm using current cvs version of the kernel,
and found that SH7709A(118MHz) executes user-land
programs much faster than SH7750(200MHz).

following patch makes this things better.
my SH7750 board takes about 4.7sec when compile hello.c
before applying this patch, and 2.2sec after patch.

current __flush_page_to_ram invalidates data cache of the page,
but I think write back is sufficient.  

I'm not sure whether this patch causes synonym problem.

Is this approach correct ?

Index: arch/sh/mm/cache.c
===================================================================
RCS file: /cvsroot/linuxsh/kernel/arch/sh/mm/cache.c,v
retrieving revision 1.21
diff -u -r1.21 cache.c
--- arch/sh/mm/cache.c  2000/09/18 05:15:35     1.21
+++ arch/sh/mm/cache.c  2000/12/02 14:38:14
@@ -397,22 +397,21 @@
  */
 void __flush_page_to_ram(void *kaddr)
 {
-       unsigned long phys, addr, data, i;
+       unsigned long v;

-       /* Physical address of this page */
-       phys = PHYSADDR(kaddr);
-
-       jump_to_P2();
-       /* Loop all the D-cache */
-       for (i=0; i<CACHE_OC_NUM_ENTRIES; i++) {
-               addr = CACHE_OC_ADDRESS_ARRAY| (i<<CACHE_OC_ENTRY_SHIFT);
-               data = ctrl_inl(addr);
-               if ((data & CACHE_VALID) && (data&PAGE_MASK) == phys) {
-                       data &= ~(CACHE_UPDATED|CACHE_VALID);
-                       ctrl_outl(data, addr);
-               }
+       for (v = (unsigned long)kaddr; v < (unsigned long)kaddr+PAGE_SIZE; ) {
+               asm volatile(
+                       "ocbwb  @%0\n\t"
+                       "add    %2,%0\n\t"
+                       "ocbwb  @%0\n\t"
+                       "add    %2,%0\n\t"
+                       "ocbwb  @%0\n\t"
+                       "add    %2,%0\n\t"
+                       "ocbwb  @%0\n\t"
+                       "add    %2,%0\n\t"
+                       : "=r"(v)
+                       : "0" (v), "r"(L1_CACHE_BYTES));
        }
-       back_to_P1();
 }

 void flush_page_to_ram(struct page *pg)


-----
SUGIOKA Toshinobu