Re: [PATCH V4 01/13] perf/core, x86: Add PERF_SAMPLE_DATA_PAGE_SIZE

Peter Zijlstra
2019-02-01T12:47:53Z

On Fri, Feb 01, 2019 at 01:43:48PM +0100, Peter Zijlstra wrote:

> static u64 __perf_get_page_size(struct mm_struct *mm, unsigned long addr)
> {
> pgd_t *pgd;
> p4d_t *p4d;
> pud_t *pud;
> pmd_t *pmd;
> pte_t *pte;
>
> pgd = pgd_offset(mm, addr);
> if (pgd_none(*pgd))
> return 0;
>
> p4d = p4d_offset(pgd, addr);
> if (!p4d_present(*p4d))
> return 0;
>
> if (p4d_large(*p4d)) {
> struct page *page = p4d_page(*p4d);
> int shift = P4D_SHIFT;
>
> if (PageHuge(page)) {
> page = compound_head(page);
> shift = PAGE_SHIFT + compound_order(page);
> }
>
> return 1ULL << shift;
> }
>
> if (!p4d_present(*p4d))
> return 0;
>
> pud = pud_offset(p4d, addr);
> if (!pud_present(*pud))
> return 0;
>
> if (pud_large(*pud)) {
> struct page *page = pud_page(*pud);
> int shift = P4D_SHIFT;

PUD_SHIFT

>
> if (PageHuge(page)) {
> page = compound_head(page);
> shift = PAGE_SHIFT + compound_order(page);
> }
>
> return 1ULL << shift;
> }
>
> pmd = pmd_offset(pud, addr);
> if (!pmd_present(*pmd))
> return 0;
>
> if (pmd_large(*pmd)) {
> struct page *page = pud_page(*pud);
> int shift = P4D_SHIFT;

PMD_SHIFT

>
> if (PageHuge(page)) {
> page = compound_head(page);
> shift = PAGE_SHIFT + compound_order(page);
> }
>
> return 1ULL << shift;
> }
>
> pte = pte_offset_map(pmd, addr);
> if (!pte_present(*pte)) {
> pte_unmap(pte);
> return 0;
> }
>
> pte_unmap(pte);
> return PAGE_SIZE;
> }