s390/mm: zero page cache synonyms for zEC12

To avoid cache synonyms on System zEC12 32 independent zero pages are
required, one for each combination for bits 2**12 to 2**16 of the virtual
address. To avoid wasting too much memory on small virtual systems the
number of zero pages is limited to 4 if the memory size is less or equal
to 64MB.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 49ce6bb2c641..9f9c315b4c07 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -63,10 +63,18 @@ static unsigned long __init setup_zero_pages(void)
                 break;
         case 0x2097:    /* z10 */
         case 0x2098:    /* z10 */
-        default:
+        case 0x2817:    /* z196 */
+        case 0x2818:    /* z196 */
                 order = 2;
                 break;
+        case 0x2827:    /* zEC12 */
+        default:
+                order = 5;
+                break;
         }
+        /* Limit number of empty zero pages for small memory sizes */
+        if (order > 2 && totalram_pages <= 16384)
+                order = 2;
 
         empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
         if (!empty_zero_page)