Messages in this thread | | | Date | Fri, 1 Feb 2019 11:03:58 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH V4 01/13] perf/core, x86: Add PERF_SAMPLE_DATA_PAGE_SIZE |
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On Fri, Feb 01, 2019 at 10:22:40AM +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; > + > + pgd = pgd_offset(mm, addr); > + if (pgd_none(*pgd)) > + return 0; > + > + p4d = p4d_offset(pgd, addr); > + if (p4d_none(*p4d)) > + return 0; > + > + if (p4d_large(*p4d)); > + return 1ULL << P4D_SHIFT; > + > + if (!p4d_present(*p4d)) > + return 0; > + > + pud = pud_offset(p4d, addr); > + if (pud_none(*pud)) > + return 0; > + > + if (pud_large(*pud)) > + return 1ULL << PUD_SHIFT;
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.
> + > + if (!pud_present(*pud)) > + return 0; > + > + pmd = pmd_offset(pud, addr); > + if (pmd_none(*pmd)) > + return 0; > + > + if (pmd_large(*pmd)) > + return 1ULL << PMD_SHIFT;
And same here I suppose..
> + > + if (!pmd_present(*pmd)) > + return 0; > + > + return 1ULL << PAGE_SHIFT; > +}
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