If the PMD is flushed then a parallel fault in handle_mm_fault() will enter the pmd_none and do_huge_pmd_anonymous_page() path where it'll attempt to insert a huge zero page. This is wasteful so the patch avoids clearing the PMD when setting pmd_numa.
Signed-off-by: Mel Gorman <[email protected]> --- mm/huge_memory.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 203b5bc..d6c3bf4 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1474,20 +1474,24 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, if (__pmd_trans_huge_lock(pmd, vma) == 1) { pmd_t entry; - entry = pmdp_get_and_clear(mm, addr, pmd); + if (!prot_numa) { + entry = pmdp_get_and_clear(mm, addr, pmd); entry = pmd_modify(entry, newprot); BUG_ON(pmd_write(entry)); + set_pmd_at(mm, addr, pmd, entry); } else { struct page *page = pmd_page(*pmd); + entry = *pmd; /* only check non-shared pages */ if (page_mapcount(page) == 1 && !pmd_numa(*pmd)) { entry = pmd_mknuma(entry); + set_pmd_at(mm, addr, pmd, entry); } } - set_pmd_at(mm, addr, pmd, entry); + spin_unlock(&vma->vm_mm->page_table_lock); ret = 1; } -- 1.8.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
