[PATCH] sparc64: Do not flush dcache for ZERO_PAGE.
This case actually can get exercised a lot during an ELF coredump of a process which contains a lot of non-COW'd anonymous pages. GDB has this test case which in partiaular creates near terabyte process full of ZERO_PAGEes. It takes forever to just walk through the page tables because of all of these spurious cache flushes on sparc64. With this change it takes only a second or so. Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -201,13 +201,24 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t p
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void flush_dcache_page(struct page *page)
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{
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struct address_space *mapping = page_mapping(page);
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int dirty = test_bit(PG_dcache_dirty, &page->flags);
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int dirty_cpu = dcache_dirty_cpu(page);
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int this_cpu = get_cpu();
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struct address_space *mapping;
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int this_cpu;
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/* Do not bother with the expensive D-cache flush if it
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* is merely the zero page. The 'bigcore' testcase in GDB
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* causes this case to run millions of times.
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*/
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if (page == ZERO_PAGE(0))
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return;
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this_cpu = get_cpu();
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mapping = page_mapping(page);
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if (mapping && !mapping_mapped(mapping)) {
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int dirty = test_bit(PG_dcache_dirty, &page->flags);
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if (dirty) {
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int dirty_cpu = dcache_dirty_cpu(page);
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if (dirty_cpu == this_cpu)
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goto out;
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smp_flush_dcache_page_impl(page, dirty_cpu);
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