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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: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2018-08-23 21:01:46 +01:00
parent 22a61c3c4f
commit a6d60245d6
2 changed files with 53 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
include/asm-generic/tlb.h
View File

@ -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,
@ -232,13 +263,19 @@ 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)); \
__tlb_remove_tlb_entry(tlb, ptep, address); \
#define tlb_remove_huge_tlb_entry(h, tlb, ptep, address) \
do { \
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)
@ -291,7 +330,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
#define pte_free_tlb(tlb, ptep, address) \
do { \
__tlb_adjust_range(tlb, address, PAGE_SIZE); \
tlb->freed_tables = 1; \
tlb->freed_tables = 1; \
tlb->cleared_pmds = 1; \
__pte_free_tlb(tlb, ptep, address); \
} while (0)
#endif
@ -300,7 +340,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
#define pmd_free_tlb(tlb, pmdp, address) \
do { \
__tlb_adjust_range(tlb, address, PAGE_SIZE); \
tlb->freed_tables = 1; \
tlb->freed_tables = 1; \
tlb->cleared_puds = 1; \
__pmd_free_tlb(tlb, pmdp, address); \
} while (0)
#endif
@ -310,7 +351,8 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
#define pud_free_tlb(tlb, pudp, address) \
do { \
__tlb_adjust_range(tlb, address, PAGE_SIZE); \
tlb->freed_tables = 1; \
tlb->freed_tables = 1; \
tlb->cleared_p4ds = 1; \
__pud_free_tlb(tlb, pudp, address); \
} while (0)
#endif
@ -321,7 +363,7 @@ static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
#define p4d_free_tlb(tlb, pudp, address) \
do { \
__tlb_adjust_range(tlb, address, PAGE_SIZE); \
tlb->freed_tables = 1; \
tlb->freed_tables = 1; \
__p4d_free_tlb(tlb, pudp, address); \
} while (0)
#endif

4
mm/memory.c
View File

@ -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);