Commit a6d60245 authored by Will Deacon's avatar Will Deacon
Browse files

asm-generic/tlb: Track which levels of the page tables have been cleared 



It is common for architectures with hugepage support to require only a
single TLB invalidation operation per hugepage during unmap(), rather than
iterating through the mapping at a PAGE_SIZE increment. Currently,
however, the level in the page table where the unmap() operation occurs
is not stored in the mmu_gather structure, therefore forcing
architectures to issue additional TLB invalidation operations or to give
up and over-invalidate by e.g. invalidating the entire TLB.

Ideally, we could add an interval rbtree to the mmu_gather structure,
which would allow us to associate the correct mapping granule with the
various sub-mappings within the range being invalidated. However, this
is costly in terms of book-keeping and memory management, so instead we
approximate by keeping track of the page table levels that are cleared
and provide a means to query the smallest granule required for invalidation.

Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 22a61c3c

include/asm-generic/tlb.h

+50 −8
Original line number Diff line number Diff line
@@ -116,6 +116,14 @@ struct mmu_gather { 
	 */

	unsigned int		freed_tables : 1;



	/*

	 * at which levels have we cleared entries?

	 */

	unsigned int		cleared_ptes : 1;

	unsigned int		cleared_pmds : 1;

	unsigned int		cleared_puds : 1;

	unsigned int		cleared_p4ds : 1;



	struct mmu_gather_batch *active;

	struct mmu_gather_batch	local;

	struct page		*__pages[MMU_GATHER_BUNDLE];
@@ -150,6 +158,10 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb) 
		tlb->end = 0;

	}

	tlb->freed_tables = 0;

	tlb->cleared_ptes = 0;

	tlb->cleared_pmds = 0;

	tlb->cleared_puds = 0;

	tlb->cleared_p4ds = 0;

}



static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
@@ -199,6 +211,25 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
}

#endif



static inline unsigned long tlb_get_unmap_shift(struct mmu_gather *tlb)

{

	if (tlb->cleared_ptes)

		return PAGE_SHIFT;

	if (tlb->cleared_pmds)

		return PMD_SHIFT;

	if (tlb->cleared_puds)

		return PUD_SHIFT;

	if (tlb->cleared_p4ds)

		return P4D_SHIFT;



	return PAGE_SHIFT;

}



static inline unsigned long tlb_get_unmap_size(struct mmu_gather *tlb)

{

	return 1UL << tlb_get_unmap_shift(tlb);

}



/*

 * In the case of tlb vma handling, we can optimise these away in the

 * case where we're doing a full MM flush.  When we're doing a munmap,
@@ -232,12 +263,18 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
#define tlb_remove_tlb_entry(tlb, ptep, address)		\

	do {							\

		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\

		tlb->cleared_ptes = 1;				\

		__tlb_remove_tlb_entry(tlb, ptep, address);	\

	} while (0)



#define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)	\

	do {							\

		__tlb_adjust_range(tlb, address, huge_page_size(h)); \

		unsigned long _sz = huge_page_size(h);		\

		__tlb_adjust_range(tlb, address, _sz);		\

		if (_sz == PMD_SIZE)				\

			tlb->cleared_pmds = 1;			\

		else if (_sz == PUD_SIZE)			\

			tlb->cleared_puds = 1;			\

		__tlb_remove_tlb_entry(tlb, ptep, address);	\

	} while (0)
@@ -252,6 +289,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
#define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)			\

	do {								\

		__tlb_adjust_range(tlb, address, HPAGE_PMD_SIZE);	\

		tlb->cleared_pmds = 1;					\

		__tlb_remove_pmd_tlb_entry(tlb, pmdp, address);		\

	} while (0)
@@ -266,6 +304,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
#define tlb_remove_pud_tlb_entry(tlb, pudp, address)			\

	do {								\

		__tlb_adjust_range(tlb, address, HPAGE_PUD_SIZE);	\

		tlb->cleared_puds = 1;					\

		__tlb_remove_pud_tlb_entry(tlb, pudp, address);		\

	} while (0)
@@ -292,6 +331,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
	do {							\

		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\

		tlb->freed_tables = 1;				\

		tlb->cleared_pmds = 1;				\

		__pte_free_tlb(tlb, ptep, address);		\

	} while (0)

#endif
@@ -301,6 +341,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
	do {							\

		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\

		tlb->freed_tables = 1;				\

		tlb->cleared_puds = 1;				\

		__pmd_free_tlb(tlb, pmdp, address);		\

	} while (0)

#endif
@@ -311,6 +352,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb, 
	do {							\

		__tlb_adjust_range(tlb, address, PAGE_SIZE);	\

		tlb->freed_tables = 1;				\

		tlb->cleared_p4ds = 1;				\

		__pud_free_tlb(tlb, pudp, address);		\

	} while (0)

#endif

mm/memory.c

+3 −1
Original line number Diff line number Diff line
@@ -267,8 +267,10 @@ void arch_tlb_finish_mmu(struct mmu_gather *tlb, 
{

	struct mmu_gather_batch *batch, *next;



	if (force)

	if (force) {

		__tlb_reset_range(tlb);

		__tlb_adjust_range(tlb, start, end - start);

	}



	tlb_flush_mmu(tlb);

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