On Fri, Sep 13, 2013 at 04:06:15PM +0300, Kirill A. Shutemov wrote:
> The basic idea is the same as with PTE level: the lock is embedded into
> struct page of table's page.
>
> Split pmd page table lock only makes sense on big machines.
> Let's say >= 32 CPUs for now.
>
> We can't use mm->pmd_huge_pte to store pgtables for THP, since we don't
> take mm->page_table_lock anymore. Let's reuse page->lru of table's page
> for that.
Looks nice.
> hugetlbfs hasn't converted to split locking: disable split locking if
> hugetlbfs enabled.
I don't think that we have to disable when hugetlbfs is enabled,
because hugetlbfs code doesn't use huge_pmd_lockptr() or huge_pmd_lock().
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 31 +++++++++++++++++++++++++++++++
> include/linux/mm_types.h | 5 +++++
> kernel/fork.c | 4 ++--
> mm/Kconfig | 10 ++++++++++
> 4 files changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index d2f8a50..5b3922d 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1294,13 +1294,44 @@ static inline void pgtable_page_dtor(struct page *page)
> ((unlikely(pmd_none(*(pmd))) && __pte_alloc_kernel(pmd, address))? \
> NULL: pte_offset_kernel(pmd, address))
>
> +#if USE_SPLIT_PMD_PTLOCKS
> +
> +static inline spinlock_t *huge_pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
> +{
> + return &virt_to_page(pmd)->ptl;
> +}
> +
> +static inline void pgtable_pmd_page_ctor(struct page *page)
> +{
> + spin_lock_init(&page->ptl);
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + page->pmd_huge_pte = NULL;
> +#endif
> +}
> +
> +static inline void pgtable_pmd_page_dtor(struct page *page)
> +{
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + VM_BUG_ON(page->pmd_huge_pte);
> +#endif
> +}
> +
> +#define pmd_huge_pte(mm, pmd) (virt_to_page(pmd)->pmd_huge_pte)
>
> +
> +#else
> +
> static inline spinlock_t *huge_pmd_lockptr(struct mm_struct *mm, pmd_t *pmd)
> {
> return &mm->page_table_lock;
> }
>
> +static inline void pgtable_pmd_page_ctor(struct page *page) {}
> +static inline void pgtable_pmd_page_dtor(struct page *page) {}
> +
> #define pmd_huge_pte(mm, pmd) ((mm)->pmd_huge_pte)
>
> +#endif
> +
> static inline spinlock_t *huge_pmd_lock(struct mm_struct *mm, pmd_t *pmd)
> {
> spinlock_t *ptl = huge_pmd_lockptr(mm, pmd);
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 1c64730..5706ddf 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -24,6 +24,8 @@
> struct address_space;
>
> #define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTE_PTLOCK_CPUS)
> +#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
> + NR_CPUS >= CONFIG_SPLIT_PMD_PTLOCK_CPUS)
>
> /*
> * Each physical page in the system has a struct page associated with
> @@ -130,6 +132,9 @@ struct page {
>
> struct list_head list; /* slobs list of pages */
> struct slab *slab_page; /* slab fields */
> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
> + pgtable_t pmd_huge_pte; /* protected by page->ptl */
> +#endif
> };
>
> /* Remainder is not double word aligned */
Can we remove pmd_huge_pte from mm_struct when USE_SPLIT_PMD_PTLOCKS is true?
Thanks,
Naoya Horiguchi
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