um: Remove unnecessary faulted check in uaccess.c (747b254c) · Commits · 戴 / test

It is not necessary to check if a fault has occured or not after disabling pagefaults. kmap_atomic does that in all cases and we can disable it for 64 bit where kmap is not needed and a simple page_address would suffice. dd if=/dev/zero of=/dev/null bs=1M count=1M Before: 3.1GB/s. After: 3.5GB/s There is a noticeable difference for file disk read and write as well as less noticeable difference for network IO. Signed-off-by:

Anton Ivanov <anton.ivanov@cambridgegreys.com> Signed-off-by:

Richard Weinberger <richard@nod.at>

arch/um/kernel/skas/uaccess.c

+12 −11

Original line number	Diff line number	Diff line
		@@ -62,27 +62,28 @@ static int do_op_one_page(unsigned long addr, int len, int is_write,
		jmp_buf buf;
		struct page *page;
		pte_t *pte;
		int n, faulted;
		int n;

		pte = maybe_map(addr, is_write);
		if (pte == NULL)
		return -1;

		page = pte_page(*pte);
		#ifdef CONFIG_64BIT
		pagefault_disable();
		addr = (unsigned long) page_address(page) +
		(addr & ~PAGE_MASK);
		#else
		addr = (unsigned long) kmap_atomic(page) +
		(addr & ~PAGE_MASK);

		current->thread.fault_catcher = &buf;

		faulted = UML_SETJMP(&buf);
		if (faulted == 0)
		#endif
		n = (*op)(addr, len, arg);
		else
		n = -1;

		current->thread.fault_catcher = NULL;

		#ifdef CONFIG_64BIT
		pagefault_enable();
		#else
		kunmap_atomic((void *)addr);
		#endif

		return n;
		}

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