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Commit 238ec4ef authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Martin Schwidefsky
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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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 229aebb8

arch/s390/include/asm/pgtable.h

+19 −3
Original line number Diff line number Diff line
@@ -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__ */



/*

arch/s390/mm/init.c

+45 −4
Original line number Diff line number Diff line
@@ -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;