Commit c16af121 authored by Wang Kefeng's avatar Wang Kefeng Committed by Russell King (Oracle)
Browse files

ARM: 9328/1: mm: try VMA lock-based page fault handling first 



Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails, the ebizzy benchmark
shows 25% improvement on qemu with 2 cpus.

Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
parent b85ea95d

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ config ARM 
	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7

	select ARCH_SUPPORTS_ATOMIC_RMW

	select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE

	select ARCH_SUPPORTS_PER_VMA_LOCK

	select ARCH_USE_BUILTIN_BSWAP

	select ARCH_USE_CMPXCHG_LOCKREF

	select ARCH_USE_MEMTEST

arch/arm/mm/fault.c

+30 −0
Original line number Diff line number Diff line
@@ -278,6 +278,35 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 


	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);



	if (!(flags & FAULT_FLAG_USER))

		goto lock_mmap;



	vma = lock_vma_under_rcu(mm, addr);

	if (!vma)

		goto lock_mmap;



	if (!(vma->vm_flags & vm_flags)) {

		vma_end_read(vma);

		goto lock_mmap;

	}

	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);

	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))

		vma_end_read(vma);



	if (!(fault & VM_FAULT_RETRY)) {

		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);

		goto done;

	}

	count_vm_vma_lock_event(VMA_LOCK_RETRY);



	/* Quick path to respond to signals */

	if (fault_signal_pending(fault, regs)) {

		if (!user_mode(regs))

			goto no_context;

		return 0;

	}

lock_mmap:



retry:

	vma = lock_mm_and_find_vma(mm, addr, regs);

	if (unlikely(!vma)) {
@@ -316,6 +345,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 
	}



	mmap_read_unlock(mm);

done:



	/*

	 * Handle the "normal" case first - VM_FAULT_MAJOR