Commit d10e63f2 authored by Mel Gorman's avatar Mel Gorman
Browse files

mm: numa: Create basic numa page hinting infrastructure 



Note: This patch started as "mm/mpol: Create special PROT_NONE
	infrastructure" and preserves the basic idea but steals *very*
	heavily from "autonuma: numa hinting page faults entry points" for
	the actual fault handlers without the migration parts.	The end
	result is barely recognisable as either patch so all Signed-off
	and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with
	this version, I will re-add the signed-offs-by to reflect the history.

In order to facilitate a lazy -- fault driven -- migration of pages, create
a special transient PAGE_NUMA variant, we can then use the 'spurious'
protection faults to drive our migrations from.

The meaning of PAGE_NUMA depends on the architecture but on x86 it is
effectively PROT_NONE. Actual PROT_NONE mappings will not generate these
NUMA faults for the reason that the page fault code checks the permission on
the VMA (and will throw a segmentation fault on actual PROT_NONE mappings),
before it ever calls handle_mm_fault.

[dhillf@gmail.com: Fix typo]
Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
parent 1ba6e0b5

include/linux/huge_mm.h

+10 −0
Original line number Diff line number Diff line
@@ -159,6 +159,10 @@ static inline struct page *compound_trans_head(struct page *page) 
	}

	return page;

}



extern int do_huge_pmd_numa_page(struct mm_struct *mm, unsigned long addr,

				  pmd_t pmd, pmd_t *pmdp);



#else /* CONFIG_TRANSPARENT_HUGEPAGE */

#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })

#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -195,6 +199,12 @@ static inline int pmd_trans_huge_lock(pmd_t *pmd, 
{

	return 0;

}



static inline int do_huge_pmd_numa_page(struct mm_struct *mm, unsigned long addr,

					pmd_t pmd, pmd_t *pmdp)

{

}



#endif /* CONFIG_TRANSPARENT_HUGEPAGE */



#endif /* _LINUX_HUGE_MM_H */

mm/huge_memory.c

+22 −0
Original line number Diff line number Diff line
@@ -1018,6 +1018,28 @@ out: 
	return page;

}



/* NUMA hinting page fault entry point for trans huge pmds */

int do_huge_pmd_numa_page(struct mm_struct *mm, unsigned long addr,

				pmd_t pmd, pmd_t *pmdp)

{

	struct page *page;

	unsigned long haddr = addr & HPAGE_PMD_MASK;



	spin_lock(&mm->page_table_lock);

	if (unlikely(!pmd_same(pmd, *pmdp)))

		goto out_unlock;



	page = pmd_page(pmd);

	pmd = pmd_mknonnuma(pmd);

	set_pmd_at(mm, haddr, pmdp, pmd);

	VM_BUG_ON(pmd_numa(*pmdp));

	update_mmu_cache_pmd(vma, addr, pmdp);



out_unlock:

	spin_unlock(&mm->page_table_lock);

	return 0;

}



int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,

		 pmd_t *pmd, unsigned long addr)

{

mm/memory.c

+109 −3
Original line number Diff line number Diff line
@@ -3448,6 +3448,103 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma, 
	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);

}



int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

		   unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)

{

	struct page *page;

	spinlock_t *ptl;



	/*

	* The "pte" at this point cannot be used safely without

	* validation through pte_unmap_same(). It's of NUMA type but

	* the pfn may be screwed if the read is non atomic.

	*

	* ptep_modify_prot_start is not called as this is clearing

	* the _PAGE_NUMA bit and it is not really expected that there

	* would be concurrent hardware modifications to the PTE.

	*/

	ptl = pte_lockptr(mm, pmd);

	spin_lock(ptl);

	if (unlikely(!pte_same(*ptep, pte)))

		goto out_unlock;

	pte = pte_mknonnuma(pte);

	set_pte_at(mm, addr, ptep, pte);

	update_mmu_cache(vma, addr, ptep);



	page = vm_normal_page(vma, addr, pte);

	if (!page) {

		pte_unmap_unlock(ptep, ptl);

		return 0;

	}



out_unlock:

	pte_unmap_unlock(ptep, ptl);

	return 0;

}



/* NUMA hinting page fault entry point for regular pmds */

#ifdef CONFIG_NUMA_BALANCING

static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

		     unsigned long addr, pmd_t *pmdp)

{

	pmd_t pmd;

	pte_t *pte, *orig_pte;

	unsigned long _addr = addr & PMD_MASK;

	unsigned long offset;

	spinlock_t *ptl;

	bool numa = false;



	spin_lock(&mm->page_table_lock);

	pmd = *pmdp;

	if (pmd_numa(pmd)) {

		set_pmd_at(mm, _addr, pmdp, pmd_mknonnuma(pmd));

		numa = true;

	}

	spin_unlock(&mm->page_table_lock);



	if (!numa)

		return 0;



	/* we're in a page fault so some vma must be in the range */

	BUG_ON(!vma);

	BUG_ON(vma->vm_start >= _addr + PMD_SIZE);

	offset = max(_addr, vma->vm_start) & ~PMD_MASK;

	VM_BUG_ON(offset >= PMD_SIZE);

	orig_pte = pte = pte_offset_map_lock(mm, pmdp, _addr, &ptl);

	pte += offset >> PAGE_SHIFT;

	for (addr = _addr + offset; addr < _addr + PMD_SIZE; pte++, addr += PAGE_SIZE) {

		pte_t pteval = *pte;

		struct page *page;

		if (!pte_present(pteval))

			continue;

		if (!pte_numa(pteval))

			continue;

		if (addr >= vma->vm_end) {

			vma = find_vma(mm, addr);

			/* there's a pte present so there must be a vma */

			BUG_ON(!vma);

			BUG_ON(addr < vma->vm_start);

		}

		if (pte_numa(pteval)) {

			pteval = pte_mknonnuma(pteval);

			set_pte_at(mm, addr, pte, pteval);

		}

		page = vm_normal_page(vma, addr, pteval);

		if (unlikely(!page))

			continue;

	}

	pte_unmap_unlock(orig_pte, ptl);



	return 0;

}

#else

static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

		     unsigned long addr, pmd_t *pmdp)

{

	BUG();

}

#endif /* CONFIG_NUMA_BALANCING */



/*

 * These routines also need to handle stuff like marking pages dirty

 * and/or accessed for architectures that don't do it in hardware (most
@@ -3486,6 +3583,9 @@ int handle_pte_fault(struct mm_struct *mm, 
					pte, pmd, flags, entry);

	}



	if (pte_numa(entry))

		return do_numa_page(mm, vma, address, entry, pte, pmd);



	ptl = pte_lockptr(mm, pmd);

	spin_lock(ptl);

	if (unlikely(!pte_same(*pte, entry)))
@@ -3554,9 +3654,11 @@ retry: 


		barrier();

		if (pmd_trans_huge(orig_pmd)) {

			if (flags & FAULT_FLAG_WRITE &&

			    !pmd_write(orig_pmd) &&

			    !pmd_trans_splitting(orig_pmd)) {

			if (pmd_numa(*pmd))

				return do_huge_pmd_numa_page(mm, address,

							     orig_pmd, pmd);



			if ((flags & FAULT_FLAG_WRITE) && !pmd_write(orig_pmd)) {

				ret = do_huge_pmd_wp_page(mm, vma, address, pmd,

							  orig_pmd);

				/*
@@ -3568,10 +3670,14 @@ retry: 
					goto retry;

				return ret;

			}



			return 0;

		}

	}



	if (pmd_numa(*pmd))

		return do_pmd_numa_page(mm, vma, address, pmd);



	/*

	 * Use __pte_alloc instead of pte_alloc_map, because we can't

	 * run pte_offset_map on the pmd, if an huge pmd could

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