Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> writes:
> Currently all of page table handling by hugetlbfs code are done under
> mm->page_table_lock. So when a process have many threads and they heavily
> access to the memory, lock contention happens and impacts the performance.
>
> This patch makes hugepage support split page table lock so that we use
> page->ptl of the leaf node of page table tree which is pte for normal pages
> but can be pmd and/or pud for hugepages of some architectures.
>
> ChangeLog v2:
> - add split ptl on other archs missed in v1
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> ---
> arch/powerpc/mm/hugetlbpage.c | 6 ++-
> arch/tile/mm/hugetlbpage.c | 6 ++-
> include/linux/hugetlb.h | 20 ++++++++++
> mm/hugetlb.c | 92 ++++++++++++++++++++++++++-----------------
> mm/mempolicy.c | 5 ++-
> mm/migrate.c | 4 +-
> mm/rmap.c | 2 +-
> 7 files changed, 90 insertions(+), 45 deletions(-)
>
> diff --git v3.11-rc3.orig/arch/powerpc/mm/hugetlbpage.c v3.11-rc3/arch/powerpc/mm/hugetlbpage.c
> index d67db4b..7e56cb7 100644
> --- v3.11-rc3.orig/arch/powerpc/mm/hugetlbpage.c
> +++ v3.11-rc3/arch/powerpc/mm/hugetlbpage.c
> @@ -124,6 +124,7 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
> {
> struct kmem_cache *cachep;
> pte_t *new;
> + spinlock_t *ptl;
>
> #ifdef CONFIG_PPC_FSL_BOOK3E
> int i;
> @@ -141,7 +142,8 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
> if (! new)
> return -ENOMEM;
>
> - spin_lock(&mm->page_table_lock);
> + ptl = huge_pte_lockptr(mm, new);
> + spin_lock(ptl);
Are you sure we can do that for ppc ?
new = kmem_cache_zalloc(cachep, GFP_KERNEL|__GFP_REPEAT);
The page for new(pte_t) could be shared right ? which mean a deadlock ?
May be you should do it at the pmd level itself for ppc
> #ifdef CONFIG_PPC_FSL_BOOK3E
> /*
> * We have multiple higher-level entries that point to the same
> @@ -174,7 +176,7 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
> #endif
> }
> #endif
> - spin_unlock(&mm->page_table_lock);
> + spin_unlock(ptl);
> return 0;
> }
>
-aneesh
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