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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
[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>
authored by
Martin Schwidefsky
and committed by
Martin Schwidefsky
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arch/s390/include/asm/pgtable.h
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arch/s390/include/asm/pgtable.h
···
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#define update_mmu_cache(vma, address, ptep) do { } while (0)
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/*
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* ZERO_PAGE is a global shared page that is always zero: used
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* ZERO_PAGE is a global shared page that is always zero; used
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* for zero-mapped memory areas etc..
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*/
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extern char empty_zero_page[PAGE_SIZE];
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#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
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extern unsigned long empty_zero_page;
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extern unsigned long zero_page_mask;
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#define ZERO_PAGE(vaddr) \
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(virt_to_page((void *)(empty_zero_page + \
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(((unsigned long)(vaddr)) &zero_page_mask))))
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#define is_zero_pfn is_zero_pfn
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static inline int is_zero_pfn(unsigned long pfn)
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{
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extern unsigned long zero_pfn;
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unsigned long offset_from_zero_pfn = pfn - zero_pfn;
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return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
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}
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#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))
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#endif /* !__ASSEMBLY__ */
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/*
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arch/s390/mm/init.c
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arch/s390/mm/init.c
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pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((__aligned__(PAGE_SIZE)));
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char empty_zero_page[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
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unsigned long empty_zero_page, zero_page_mask;
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EXPORT_SYMBOL(empty_zero_page);
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static unsigned long setup_zero_pages(void)
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{
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struct cpuid cpu_id;
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unsigned int order;
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unsigned long size;
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struct page *page;
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int i;
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get_cpu_id(&cpu_id);
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switch (cpu_id.machine) {
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case 0x9672: /* g5 */
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case 0x2064: /* z900 */
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case 0x2066: /* z900 */
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case 0x2084: /* z990 */
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case 0x2086: /* z990 */
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case 0x2094: /* z9-109 */
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case 0x2096: /* z9-109 */
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order = 0;
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break;
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case 0x2097: /* z10 */
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case 0x2098: /* z10 */
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default:
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order = 2;
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break;
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}
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empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
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if (!empty_zero_page)
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panic("Out of memory in setup_zero_pages");
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page = virt_to_page((void *) empty_zero_page);
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split_page(page, order);
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for (i = 1 << order; i > 0; i--) {
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SetPageReserved(page);
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page++;
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}
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size = PAGE_SIZE << order;
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zero_page_mask = (size - 1) & PAGE_MASK;
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return 1UL << order;
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}
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/*
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* paging_init() sets up the page tables
···
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max_mapnr = num_physpages = max_low_pfn;
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high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
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/* clear the zero-page */
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memset(empty_zero_page, 0, PAGE_SIZE);
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/* Setup guest page hinting */
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cmma_init();
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/* this will put all low memory onto the freelists */
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totalram_pages += free_all_bootmem();
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totalram_pages -= setup_zero_pages(); /* Setup zeroed pages. */
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reservedpages = 0;
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