[PATCH] sparc64: Do not flush dcache for ZERO_PAGE. (a9546f59) · Commits · 戴 / test

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>

arch/sparc64/mm/init.c

+15 −4

Original line number	Diff line number	Diff line
		@@ -201,13 +201,24 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t p

		void flush_dcache_page(struct page *page)
		{
		struct address_space *mapping = page_mapping(page);
		int dirty = test_bit(PG_dcache_dirty, &page->flags);
		int dirty_cpu = dcache_dirty_cpu(page);
		int this_cpu = get_cpu();
		struct address_space *mapping;
		int this_cpu;

		/* Do not bother with the expensive D-cache flush if it
		* is merely the zero page. The 'bigcore' testcase in GDB
		* causes this case to run millions of times.
		*/
		if (page == ZERO_PAGE(0))
		return;

		this_cpu = get_cpu();

		mapping = page_mapping(page);
		if (mapping && !mapping_mapped(mapping)) {
		int dirty = test_bit(PG_dcache_dirty, &page->flags);
		if (dirty) {
		int dirty_cpu = dcache_dirty_cpu(page);

		if (dirty_cpu == this_cpu)
		goto out;
		smp_flush_dcache_page_impl(page, dirty_cpu);

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