Eric Lee / smarc-fsl-linux-kernel

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Commit 238ec4efeee4461d5cff2ed3e5a15a3ab850959b

Authored by Martin Schwidefsky
Committed by Martin Schwidefsky
1 parent 229aebb873

[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>

Showing 2 changed files with 64 additions and 7 deletions Side-by-side Diff

arch/s390/include/asm/pgtable.h
Diff comments   View file @ 238ec4e
... ... @@ -46,11 +46,27 @@
46 46 #define update_mmu_cache(vma, address, ptep) do { } while (0)
47 47  
48 48 /*
49   - * ZERO_PAGE is a global shared page that is always zero: used
  49 + * ZERO_PAGE is a global shared page that is always zero; used
50 50 * for zero-mapped memory areas etc..
51 51 */
52   -extern char empty_zero_page[PAGE_SIZE];
53   -#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
  52 +
  53 +extern unsigned long empty_zero_page;
  54 +extern unsigned long zero_page_mask;
  55 +
  56 +#define ZERO_PAGE(vaddr) \
  57 + (virt_to_page((void *)(empty_zero_page + \
  58 + (((unsigned long)(vaddr)) &zero_page_mask))))
  59 +
  60 +#define is_zero_pfn is_zero_pfn
  61 +static inline int is_zero_pfn(unsigned long pfn)
  62 +{
  63 + extern unsigned long zero_pfn;
  64 + unsigned long offset_from_zero_pfn = pfn - zero_pfn;
  65 + return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
  66 +}
  67 +
  68 +#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))
  69 +
54 70 #endif /* !__ASSEMBLY__ */
55 71  
56 72 /*
... ... @@ -42,9 +42,52 @@
42 42  
43 43 pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
44 44  
45   -char empty_zero_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
  45 +unsigned long empty_zero_page, zero_page_mask;
46 46 EXPORT_SYMBOL(empty_zero_page);
47 47  
  48 +static unsigned long setup_zero_pages(void)
  49 +{
  50 + struct cpuid cpu_id;
  51 + unsigned int order;
  52 + unsigned long size;
  53 + struct page *page;
  54 + int i;
  55 +
  56 + get_cpu_id(&cpu_id);
  57 + switch (cpu_id.machine) {
  58 + case 0x9672: /* g5 */
  59 + case 0x2064: /* z900 */
  60 + case 0x2066: /* z900 */
  61 + case 0x2084: /* z990 */
  62 + case 0x2086: /* z990 */
  63 + case 0x2094: /* z9-109 */
  64 + case 0x2096: /* z9-109 */
  65 + order = 0;
  66 + break;
  67 + case 0x2097: /* z10 */
  68 + case 0x2098: /* z10 */
  69 + default:
  70 + order = 2;
  71 + break;
  72 + }
  73 +
  74 + empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
  75 + if (!empty_zero_page)
  76 + panic("Out of memory in setup_zero_pages");
  77 +
  78 + page = virt_to_page((void *) empty_zero_page);
  79 + split_page(page, order);
  80 + for (i = 1 << order; i > 0; i--) {
  81 + SetPageReserved(page);
  82 + page++;
  83 + }
  84 +
  85 + size = PAGE_SIZE << order;
  86 + zero_page_mask = (size - 1) & PAGE_MASK;
  87 +
  88 + return 1UL << order;
  89 +}
  90 +
48 91 /*
49 92 * paging_init() sets up the page tables
50 93 */
51 94  
... ... @@ -92,14 +135,12 @@
92 135 max_mapnr = num_physpages = max_low_pfn;
93 136 high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
94 137  
95   - /* clear the zero-page */
96   - memset(empty_zero_page, 0, PAGE_SIZE);
97   -
98 138 /* Setup guest page hinting */
99 139 cmma_init();
100 140  
101 141 /* this will put all low memory onto the freelists */
102 142 totalram_pages += free_all_bootmem();
  143 + totalram_pages -= setup_zero_pages(); /* Setup zeroed pages. */
103 144  
104 145 reservedpages = 0;
105 146