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Commit ad3023ac authored by Mahendran Ganesh's avatar Mahendran Ganesh Committed by Vinayak Menon
Browse files

arm64/mm: add speculative page fault 



This patch enables the speculative page fault on the arm64
architecture.

I completed spf porting in 4.9. From the test result,
we can see app launching time improved by about 10% in average.
For the apps which have more than 50 threads, 15% or even more
improvement can be got.

Signed-off-by: default avatarGanesh Mahendran <opensource.ganesh@gmail.com>
Change-Id: Ib7c8b2e354800b5023e6c6400448a6d40aaf89c8
Patch-mainline: linux-mm @ Wed, 2 May 2018 15:54:32
[vinmenon@codeaurora.org: remove the speculative fault perf counter]
Signed-off-by: default avatarVinayak Menon <vinmenon@codeaurora.org>
[charante@codeaurora.org: trivial merge conflict fixes]
Signed-off-by: default avatarCharan Teja Reddy <charante@codeaurora.org>
parent bcca0756

arch/arm64/mm/fault.c

+23 −3
Original line number Diff line number Diff line
@@ -406,10 +406,9 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re 
#define VM_FAULT_BADMAP		0x010000

#define VM_FAULT_BADACCESS	0x020000



static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr,

static int __do_page_fault(struct vm_area_struct *vma, unsigned long addr,

			   unsigned int mm_flags, unsigned long vm_flags)

{

	struct vm_area_struct *vma = find_vma(mm, addr);



	if (unlikely(!vma))

		return VM_FAULT_BADMAP;
@@ -456,6 +455,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 
	vm_fault_t fault, major = 0;

	unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;

	unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

	struct vm_area_struct *vma = NULL;



	if (kprobe_page_fault(regs, esr))

		return 0;
@@ -495,6 +495,14 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 


	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);



	/*

	 * let's try a speculative page fault without grabbing the

	 * mmap_sem.

	 */

	fault = handle_speculative_fault(mm, addr, mm_flags, &vma);

	if (fault != VM_FAULT_RETRY)

		goto done;



	/*

	 * As per x86, we may deadlock here. However, since the kernel only

	 * validly references user space from well defined areas of the code,
@@ -519,7 +527,10 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 
#endif

	}



	fault = __do_page_fault(mm, addr, mm_flags, vm_flags);

	if (!vma || !can_reuse_spf_vma(vma, addr))

		vma = find_vma(mm, addr);



	fault = __do_page_fault(vma, addr, mm_flags, vm_flags);

	major |= fault & VM_FAULT_MAJOR;



	if (fault & VM_FAULT_RETRY) {
@@ -542,11 +553,20 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 
		if (mm_flags & FAULT_FLAG_ALLOW_RETRY) {

			mm_flags &= ~FAULT_FLAG_ALLOW_RETRY;

			mm_flags |= FAULT_FLAG_TRIED;



			/*

			 * Do not try to reuse this vma and fetch it

			 * again since we will release the mmap_sem.

			 */

			vma = NULL;



			goto retry;

		}

	}

	up_read(&mm->mmap_sem);



done:



	/*

	 * Handle the "normal" (no error) case first.

	 */