Messages in this thread |  | | Date | Fri, 1 Feb 2019 13:43:48 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH V4 01/13] perf/core, x86: Add PERF_SAMPLE_DATA_PAGE_SIZE |
| |
On Fri, Feb 01, 2019 at 01:36:00PM +0300, Kirill A. Shutemov wrote: > On Fri, Feb 01, 2019 at 11:03:58AM +0100, Peter Zijlstra wrote:
> > Will just mentioned a lovely feature where some archs have multi entry > > large pages. > > > > Possible something like: > > > > if (pud_large(*pud)) { > > struct page *page = pud_page(*pud); > > int order = PUD_SHIFT; > > > > if (PageHuge(page)) { > > page = compound_head(page); > > order += compound_order(page); > > } > > > > return 1ULL << order; > > } > > > > works correctly. > > For more fun: some compound pages can be mapped withe page table entries > not matching it's compound size, i.e. 2M pages mapped with PTE.
Surely not for PageHuge() ?! I thought the point of hugetlbfs was to guarantee page granularity.
How is the below?
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;
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;
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; }
|  |