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[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>
This commit is contained in:
Martin Schwidefsky 2010-10-25 16:10:07 +02:00 committed by Martin Schwidefsky
parent 229aebb873
commit 238ec4efee
2 changed files with 64 additions and 7 deletions
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22
arch/s390/include/asm/pgtable.h
View File

@ -46,11 +46,27 @@ extern void vmem_map_init(void);
#define update_mmu_cache(vma, address, ptep) do { } while (0)
/*
* ZERO_PAGE is a global shared page that is always zero: used
* ZERO_PAGE is a global shared page that is always zero; used
* for zero-mapped memory areas etc..
*/
extern char empty_zero_page[PAGE_SIZE];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
extern unsigned long empty_zero_page;
extern unsigned long zero_page_mask;
#define ZERO_PAGE(vaddr) \
(virt_to_page((void *)(empty_zero_page + \
(((unsigned long)(vaddr)) &zero_page_mask))))
#define is_zero_pfn is_zero_pfn
static inline int is_zero_pfn(unsigned long pfn)
{
extern unsigned long zero_pfn;
unsigned long offset_from_zero_pfn = pfn - zero_pfn;
return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
}
#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))
#endif /* !__ASSEMBLY__ */
/*

49
arch/s390/mm/init.c
View File

@ -42,9 +42,52 @@ DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
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 @@ void __init mem_init(void)
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;