On Tue, 9 Feb 2016 21:41:44 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote: > With next generation power processor, we are having a new mmu model > [1] that require us to maintain a different linux page table format. > > Inorder to support both current and future ppc64 systems with a single > kernel we need to make sure kernel can select between different page > table format at runtime. With the new MMU (radix MMU) added, we will > have two different pmd hugepage size 16MB for hash model and 2MB for > Radix model. Hence make HPAGE_PMD related values as a variable. > > [1] http://ibm.biz/power-isa3 (Needs registration). > > ... > > --- a/include/linux/bug.h > +++ b/include/linux/bug.h > @@ -20,6 +20,7 @@ struct pt_regs; > #define BUILD_BUG_ON_MSG(cond, msg) (0) > #define BUILD_BUG_ON(condition) (0) > #define BUILD_BUG() (0) > +#define MAYBE_BUILD_BUG_ON(cond) (0) > #else /* __CHECKER__ */ > > /* Force a compilation error if a constant expression is not a power of 2 */ > @@ -83,6 +84,14 @@ struct pt_regs; > */ > #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > > +#define MAYBE_BUILD_BUG_ON(cond) \ > + do { \ > + if (__builtin_constant_p((cond))) \ > + BUILD_BUG_ON(cond); \ > + else \ > + BUG_ON(cond); \ > + } while (0) > + hm. I suppose so. > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -111,9 +111,6 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > __split_huge_pmd(__vma, __pmd, __address); \ > } while (0) > > -#if HPAGE_PMD_ORDER >= MAX_ORDER > -#error "hugepages can't be allocated by the buddy allocator" > -#endif > extern int hugepage_madvise(struct vm_area_struct *vma, > unsigned long *vm_flags, int advice); > extern void vma_adjust_trans_huge(struct vm_area_struct *vma, > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index cd26f3f14cab..350410e9019e 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -83,7 +83,7 @@ unsigned long transparent_hugepage_flags __read_mostly = > (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); > > /* default scan 8*512 pte (or vmas) every 30 second */ > -static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; > +static unsigned int khugepaged_pages_to_scan __read_mostly; > static unsigned int khugepaged_pages_collapsed; > static unsigned int khugepaged_full_scans; > static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; > @@ -98,7 +98,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); > * it would have happened if the vma was large enough during page > * fault. > */ > -static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; > +static unsigned int khugepaged_max_ptes_none __read_mostly; > > static int khugepaged(void *none); > static int khugepaged_slab_init(void); > @@ -660,6 +660,18 @@ static int __init hugepage_init(void) > return -EINVAL; > } > > + khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; > + khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; I don't understand this change. We change the initialization from at-compile-time to at-run-time, but nothing useful appears to have been done. > + /* > + * hugepages can't be allocated by the buddy allocator > + */ > + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); > + /* > + * we use page->mapping and page->index in second tail page > + * as list_head: assuming THP order >= 2 > + */ > + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); > + > err = hugepage_init_sysfs(&hugepage_kobj); > if (err) > goto err_sysfs; > > ... > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>