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SubjectRe: [PATCH -mm] mm, hugetlb: Pass fault address to no page handler
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On 05/14/2018 05:57 PM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> This is to take better advantage of huge page clearing
> optimization (c79b57e462b5d, "mm: hugetlb: clear target sub-page last
> when clearing huge page"). Which will clear to access sub-page last
> to avoid the cache lines of to access sub-page to be evicted when
> clearing other sub-pages. This needs to get the address of the
> sub-page to access, that is, the fault address inside of the huge
> page. So the hugetlb no page fault handler is changed to pass that
> information. This will benefit workloads which don't access the begin
> of the huge page after page fault.
>
> With this patch, the throughput increases ~28.1% in vm-scalability
> anon-w-seq test case with 88 processes on a 2 socket Xeon E5 2699 v4
> system (44 cores, 88 threads). The test case creates 88 processes,
> each process mmap a big anonymous memory area and writes to it from
> the end to the begin. For each process, other processes could be seen
> as other workload which generates heavy cache pressure. At the same
> time, the cache miss rate reduced from ~36.3% to ~25.6%, the
> IPC (instruction per cycle) increased from 0.3 to 0.37, and the time
> spent in user space is reduced ~19.3%

Since this patch only addresses hugetlbfs huge pages, I would suggest
making that more explicit in the commit message. Other than that, the
changes look fine to me.

> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
--
Mike Kravetz

> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Cc: Andi Kleen <andi.kleen@intel.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Matthew Wilcox <mawilcox@microsoft.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Shaohua Li <shli@fb.com>
> Cc: Christopher Lameter <cl@linux.com>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> Cc: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> mm/hugetlb.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 129088710510..3de6326abf39 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3677,7 +3677,7 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
>
> static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> struct address_space *mapping, pgoff_t idx,
> - unsigned long address, pte_t *ptep, unsigned int flags)
> + unsigned long faddress, pte_t *ptep, unsigned int flags)
> {
> struct hstate *h = hstate_vma(vma);
> int ret = VM_FAULT_SIGBUS;
> @@ -3686,6 +3686,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> struct page *page;
> pte_t new_pte;
> spinlock_t *ptl;
> + unsigned long address = faddress & huge_page_mask(h);
>
> /*
> * Currently, we are forced to kill the process in the event the
> @@ -3749,7 +3750,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> ret = VM_FAULT_SIGBUS;
> goto out;
> }
> - clear_huge_page(page, address, pages_per_huge_page(h));
> + clear_huge_page(page, faddress, pages_per_huge_page(h));
> __SetPageUptodate(page);
> set_page_huge_active(page);
>
> @@ -3871,7 +3872,7 @@ u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
> #endif
>
> int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> - unsigned long address, unsigned int flags)
> + unsigned long faddress, unsigned int flags)
> {
> pte_t *ptep, entry;
> spinlock_t *ptl;
> @@ -3883,8 +3884,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> struct hstate *h = hstate_vma(vma);
> struct address_space *mapping;
> int need_wait_lock = 0;
> -
> - address &= huge_page_mask(h);
> + unsigned long address = faddress & huge_page_mask(h);
>
> ptep = huge_pte_offset(mm, address, huge_page_size(h));
> if (ptep) {
> @@ -3914,7 +3914,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>
> entry = huge_ptep_get(ptep);
> if (huge_pte_none(entry)) {
> - ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags);
> + ret = hugetlb_no_page(mm, vma, mapping, idx, faddress, ptep, flags);
> goto out_mutex;
> }
>
>

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