"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:
> On Tue, May 15, 2018 at 08:57:56AM +0800, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@xxxxxxxxx>
>>
>> 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%
>>
>> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
>> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>> Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
>> Cc: Jan Kara <jack@xxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
>> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
>> Cc: Minchan Kim <minchan@xxxxxxxxxx>
>> Cc: Shaohua Li <shli@xxxxxx>
>> Cc: Christopher Lameter <cl@xxxxxxxxx>
>> Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>> Cc: Punit Agrawal <punit.agrawal@xxxxxxx>
>> Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
>> ---
>> 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);
>
> faddress? I would rather keep it address and rename maked out variable to
> 'haddr'. We use 'haddr' for the cause in other places.
I found haddr is popular in huge_memory.c but not used in hugetlb.c at
all. Is it desirable to start to use "haddr" in hugetlb.c?
Best Regards,
Huang, Ying
