On Fri, Oct 28, 2022 at 02:17:01PM -0700, Mike Kravetz wrote:
On 10/28/22 12:13, Peter Xu wrote:
On Fri, Oct 28, 2022 at 08:23:25AM -0700, Mike Kravetz wrote:
On 10/26/22 21:12, Peter Xu wrote:
On Wed, Oct 26, 2022 at 04:54:01PM -0700, Mike Kravetz wrote:
On 10/26/22 17:42, Peter Xu wrote:
diff --git a/mm/madvise.c b/mm/madvise.c index c7105ec6d08c..d8b4d7e56939 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -790,7 +790,10 @@ static int madvise_free_single_vma(struct vm_area_struct *vma, static long madvise_dontneed_single_vma(struct vm_area_struct *vma, unsigned long start, unsigned long end) {
- zap_page_range(vma, start, end - start);
- if (!is_vm_hugetlb_page(vma))
zap_page_range(vma, start, end - start);- else
clear_hugetlb_page_range(vma, start, end);With the new ZAP_FLAG_UNMAP flag, clear_hugetlb_page_range() can be dropped completely? As zap_page_range() won't be with ZAP_FLAG_UNMAP so we can identify things?
IIUC that's the major reason why I thought the zap flag could be helpful..
Argh. I went to drop clear_hugetlb_page_range() but there is one issue. In zap_page_range() the MMU_NOTIFY_CLEAR notifier is certainly called. However, we really need to have a 'adjust_range_if_pmd_sharing_possible' call in there because the 'range' may be part of a shared pmd. :(
I think we need to either have a separate routine like clear_hugetlb_page_range that sets up the appropriate range, or special case hugetlb in zap_page_range. What do you think? I think clear_hugetlb_page_range is the least bad of the two options.
How about special case hugetlb as you mentioned? If I'm not wrong, it should be 3 lines change:
---8<--- diff --git a/mm/memory.c b/mm/memory.c index c5599a9279b1..0a1632e44571 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1706,11 +1706,13 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start, lru_add_drain(); mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, start, start + size); + if (is_vm_hugetlb_page(vma)) + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); tlb_gather_mmu(&tlb, vma->vm_mm); update_hiwater_rss(vma->vm_mm); mmu_notifier_invalidate_range_start(&range); do { - unmap_single_vma(&tlb, vma, start, range.end, NULL); + unmap_single_vma(&tlb, vma, start, start + size, NULL); } while ((vma = mas_find(&mas, end - 1)) != NULL); mmu_notifier_invalidate_range_end(&range); tlb_finish_mmu(&tlb); ---8<---
As zap_page_range() is already vma-oriented anyway. But maybe I missed something important?