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SubjectRe: [PATCH V3 2/2] mm: THP page cache support for ppc64
On Sun, Nov 13, 2016 at 08:30:25PM +0530, Aneesh Kumar K.V wrote:
> Add arch specific callback in the generic THP page cache code that will
> deposit and withdarw preallocated page table. Archs like ppc64 use
> this preallocated table to store the hash pte slot information.
>
> Testing:
> kernel build of the patch series on tmpfs mounted with option huge=always
>
> The related thp stat:
> thp_fault_alloc 72939
> thp_fault_fallback 60547
> thp_collapse_alloc 603
> thp_collapse_alloc_failed 0
> thp_file_alloc 253763
> thp_file_mapped 4251
> thp_split_page 51518
> thp_split_page_failed 1
> thp_deferred_split_page 73566
> thp_split_pmd 665
> thp_zero_page_alloc 3
> thp_zero_page_alloc_failed 0
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

One nit-pick below, but otherwise

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

> @@ -2975,6 +3004,13 @@ static int do_set_pmd(struct fault_env *fe, struct page *page)
> ret = 0;
> count_vm_event(THP_FILE_MAPPED);
> out:
> + /*
> + * If we are going to fallback to pte mapping, do a
> + * withdraw with pmd lock held.
> + */
> + if (arch_needs_pgtable_deposit() && (ret == VM_FAULT_FALLBACK))

Parenthesis are redundant around ret check.

> + fe->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm,
> + fe->pmd);
> spin_unlock(fe->ptl);
> return ret;
> }

--
Kirill A. Shutemov

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