[S390] zero page cache synonyms
If the zero page is mapped to virtual user space addresses that differ
only in bit 2^12 or 2^13 we get L1 cache synonyms which can affect
performance. Follow the mips model and use multiple zero pages to avoid
the synonyms.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 94b8ba2..0744fb3 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -42,9 +42,52 @@
pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
-char empty_zero_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
+unsigned long empty_zero_page, zero_page_mask;
EXPORT_SYMBOL(empty_zero_page);
+static unsigned long setup_zero_pages(void)
+{
+ struct cpuid cpu_id;
+ unsigned int order;
+ unsigned long size;
+ struct page *page;
+ int i;
+
+ get_cpu_id(&cpu_id);
+ switch (cpu_id.machine) {
+ case 0x9672: /* g5 */
+ case 0x2064: /* z900 */
+ case 0x2066: /* z900 */
+ case 0x2084: /* z990 */
+ case 0x2086: /* z990 */
+ case 0x2094: /* z9-109 */
+ case 0x2096: /* z9-109 */
+ order = 0;
+ break;
+ case 0x2097: /* z10 */
+ case 0x2098: /* z10 */
+ default:
+ order = 2;
+ break;
+ }
+
+ empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
+ if (!empty_zero_page)
+ panic("Out of memory in setup_zero_pages");
+
+ page = virt_to_page((void *) empty_zero_page);
+ split_page(page, order);
+ for (i = 1 << order; i > 0; i--) {
+ SetPageReserved(page);
+ page++;
+ }
+
+ size = PAGE_SIZE << order;
+ zero_page_mask = (size - 1) & PAGE_MASK;
+
+ return 1UL << order;
+}
+
/*
* paging_init() sets up the page tables
*/
@@ -92,14 +135,12 @@
max_mapnr = num_physpages = max_low_pfn;
high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
- /* clear the zero-page */
- memset(empty_zero_page, 0, PAGE_SIZE);
-
/* Setup guest page hinting */
cmma_init();
/* this will put all low memory onto the freelists */
totalram_pages += free_all_bootmem();
+ totalram_pages -= setup_zero_pages(); /* Setup zeroed pages. */
reservedpages = 0;