The zero page is not replicated between nodes and is often shared between processes. The data is read-only and likely to be cached in local CPUs if heavily accessed meaning that the remote memory access cost is less of a concern. This patch stops accounting for numa hinting faults on the zero page in both terms of counting faults and scheduling tasks on nodes.
[[email protected]: Correct use of is_huge_zero_page] Signed-off-by: Mel Gorman <[email protected]> --- mm/huge_memory.c | 9 +++++++++ mm/memory.c | 7 ++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e52c131..4ebe3aa 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1301,6 +1301,15 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out_unlock; page = pmd_page(pmd); + + /* + * Do not account for faults against the huge zero page. The read-only + * data is likely to be read-cached on the local CPUs and it is less + * useful to know about local versus remote hits on the zero page. + */ + if (is_huge_zero_page(page)) + goto clear_pmdnuma; + get_page(page); src_nid = numa_node_id(); count_vm_numa_event(NUMA_HINT_FAULTS); diff --git a/mm/memory.c b/mm/memory.c index 1ce2e2a..871b881 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3557,8 +3557,13 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, set_pte_at(mm, addr, ptep, pte); update_mmu_cache(vma, addr, ptep); + /* + * Do not account for faults against the zero page. The read-only data + * is likely to be read-cached on the local CPUs and it is less useful + * to know about local versus remote hits on the zero page. + */ page = vm_normal_page(vma, addr, pte); - if (!page) { + if (!page || is_zero_pfn(page_to_pfn(page))) { pte_unmap_unlock(ptep, ptl); return 0; } -- 1.8.1.4 -- 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/
