Add large folio mapping establishment support for finish_fault() as a
preparation, to support multi-size THP allocation of anonymous shmem pages
in the following patches.
Keep the same behavior (per-page fault) for non-anon shmem to avoid inflating
the RSS unintentionally, and we can discuss what size of mapping to build
when extending mTHP to control non-anon shmem in the future.
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 47 insertions(+), 10 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index eef4e482c0c2..72775ee99ff3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4831,9 +4831,12 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page;
+ struct folio *folio;
vm_fault_t ret;
bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) &&
!(vma->vm_flags & VM_SHARED);
+ int type, nr_pages;
+ unsigned long addr = vmf->address;
/* Did we COW the page? */
if (is_cow)
@@ -4864,24 +4867,58 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
return VM_FAULT_OOM;
}
+ folio = page_folio(page);
+ nr_pages = folio_nr_pages(folio);
+
+ /*
+ * Using per-page fault to maintain the uffd semantics, and same
+ * approach also applies to non-anonymous-shmem faults to avoid
+ * inflating the RSS of the process.
+ */
+ if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) {
+ nr_pages = 1;
+ } else if (nr_pages > 1) {
+ pgoff_t idx = folio_page_idx(folio, page);
+ /* The page offset of vmf->address within the VMA. */
+ pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff;
+
+ /*
+ * Fallback to per-page fault in case the folio size in page
+ * cache beyond the VMA limits.
+ */
+ if (unlikely(vma_off < idx ||
+ vma_off + (nr_pages - idx) > vma_pages(vma))) {
+ nr_pages = 1;
+ } else {
+ /* Now we can set mappings for the whole large folio. */
+ addr = vmf->address - idx * PAGE_SIZE;
+ page = &folio->page;
+ }
+ }
+
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
- vmf->address, &vmf->ptl);
+ addr, &vmf->ptl);
if (!vmf->pte)
return VM_FAULT_NOPAGE;
/* Re-check under ptl */
- if (likely(!vmf_pte_changed(vmf))) {
- struct folio *folio = page_folio(page);
- int type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
-
- set_pte_range(vmf, folio, page, 1, vmf->address);
- add_mm_counter(vma->vm_mm, type, 1);
- ret = 0;
- } else {
- update_mmu_tlb(vma, vmf->address, vmf->pte);
+ if (nr_pages == 1 && unlikely(vmf_pte_changed(vmf))) {
+ update_mmu_tlb(vma, addr, vmf->pte);
+ ret = VM_FAULT_NOPAGE;
+ goto unlock;
+ } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
+ update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
ret = VM_FAULT_NOPAGE;
+ goto unlock;
}
+ folio_ref_add(folio, nr_pages - 1);
+ set_pte_range(vmf, folio, page, nr_pages, addr);
+ type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
+ add_mm_counter(vma->vm_mm, type, nr_pages);
+ ret = 0;
+
+unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
return ret;
}
--
2.39.3
On 2024/6/11 18:11, Baolin Wang wrote:
> Add large folio mapping establishment support for finish_fault() as a
> preparation, to support multi-size THP allocation of anonymous shmem pages
> in the following patches.
>
> Keep the same behavior (per-page fault) for non-anon shmem to avoid inflating
> the RSS unintentionally, and we can discuss what size of mapping to build
> when extending mTHP to control non-anon shmem in the future.
>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
> mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 47 insertions(+), 10 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index eef4e482c0c2..72775ee99ff3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4831,9 +4831,12 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
> {
> struct vm_area_struct *vma = vmf->vma;
> struct page *page;
> + struct folio *folio;
> vm_fault_t ret;
> bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) &&
> !(vma->vm_flags & VM_SHARED);
> + int type, nr_pages;
> + unsigned long addr = vmf->address;
>
> /* Did we COW the page? */
> if (is_cow)
> @@ -4864,24 +4867,58 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
> return VM_FAULT_OOM;
> }
>
> + folio = page_folio(page);
> + nr_pages = folio_nr_pages(folio);
> +
> + /*
> + * Using per-page fault to maintain the uffd semantics, and same
> + * approach also applies to non-anonymous-shmem faults to avoid
> + * inflating the RSS of the process.
> + */
> + if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) {
> + nr_pages = 1;
> + } else if (nr_pages > 1) {
> + pgoff_t idx = folio_page_idx(folio, page);
> + /* The page offset of vmf->address within the VMA. */
> + pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff;
> +
vma->vm_pgoff
> + /*
> + * Fallback to per-page fault in case the folio size in page
> + * cache beyond the VMA limits.
> + */
> + if (unlikely(vma_off < idx ||
> + vma_off + (nr_pages - idx) > vma_pages(vma))) {
> + nr_pages = 1;
> + } else {
> + /* Now we can set mappings for the whole large folio. */
> + addr = vmf->address - idx * PAGE_SIZE;
addr -= idx * PAGE_SIZE;
> + page = &folio->page;
> + }
> + }
> +
> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
> - vmf->address, &vmf->ptl);
> + addr, &vmf->ptl);
no newline now,
> if (!vmf->pte)
> return VM_FAULT_NOPAGE;
>
> /* Re-check under ptl */
> - if (likely(!vmf_pte_changed(vmf))) {
> - struct folio *folio = page_folio(page);
> - int type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
> -
> - set_pte_range(vmf, folio, page, 1, vmf->address);
> - add_mm_counter(vma->vm_mm, type, 1);
> - ret = 0;
> - } else {
> - update_mmu_tlb(vma, vmf->address, vmf->pte);
> + if (nr_pages == 1 && unlikely(vmf_pte_changed(vmf))) {
> + update_mmu_tlb(vma, addr, vmf->pte);
> + ret = VM_FAULT_NOPAGE;
> + goto unlock;
> + } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
> + update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
> ret = VM_FAULT_NOPAGE;
> + goto unlock;
> }
We may add a vmf_pte_range_changed(), but separate it.
Some very small nits, up to you,
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> + folio_ref_add(folio, nr_pages - 1);
> + set_pte_range(vmf, folio, page, nr_pages, addr);
> + type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
> + add_mm_counter(vma->vm_mm, type, nr_pages);
> + ret = 0;
> +
> +unlock:
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> return ret;
> }
On 2024/6/12 21:40, Kefeng Wang wrote:
>
>
> On 2024/6/11 18:11, Baolin Wang wrote:
>> Add large folio mapping establishment support for finish_fault() as a
>> preparation, to support multi-size THP allocation of anonymous shmem
>> pages
>> in the following patches.
>>
>> Keep the same behavior (per-page fault) for non-anon shmem to avoid
>> inflating
>> the RSS unintentionally, and we can discuss what size of mapping to build
>> when extending mTHP to control non-anon shmem in the future.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>> mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++----------
>> 1 file changed, 47 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index eef4e482c0c2..72775ee99ff3 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4831,9 +4831,12 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>> {
>> struct vm_area_struct *vma = vmf->vma;
>> struct page *page;
>> + struct folio *folio;
>> vm_fault_t ret;
>> bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) &&
>> !(vma->vm_flags & VM_SHARED);
>> + int type, nr_pages;
>> + unsigned long addr = vmf->address;
>> /* Did we COW the page? */
>> if (is_cow)
>> @@ -4864,24 +4867,58 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>> return VM_FAULT_OOM;
>> }
>> + folio = page_folio(page);
>> + nr_pages = folio_nr_pages(folio);
>> +
>> + /*
>> + * Using per-page fault to maintain the uffd semantics, and same
>> + * approach also applies to non-anonymous-shmem faults to avoid
>> + * inflating the RSS of the process.
>> + */
>> + if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) {
>> + nr_pages = 1;
>> + } else if (nr_pages > 1) {
>> + pgoff_t idx = folio_page_idx(folio, page);
>> + /* The page offset of vmf->address within the VMA. */
>> + pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff;
>> +
> vma->vm_pgoff
>
>> + /*
>> + * Fallback to per-page fault in case the folio size in page
>> + * cache beyond the VMA limits.
>> + */
>> + if (unlikely(vma_off < idx ||
>> + vma_off + (nr_pages - idx) > vma_pages(vma))) {
>> + nr_pages = 1;
>> + } else {
>> + /* Now we can set mappings for the whole large folio. */
>> + addr = vmf->address - idx * PAGE_SIZE;
>
> addr -= idx * PAGE_SIZE;
>
>> + page = &folio->page;
>> + }
>> + }
>> +
>> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
>> - vmf->address, &vmf->ptl);
>> + addr, &vmf->ptl);
>
> no newline now,
>
>> if (!vmf->pte)
>> return VM_FAULT_NOPAGE;
>> /* Re-check under ptl */
>> - if (likely(!vmf_pte_changed(vmf))) {
>> - struct folio *folio = page_folio(page);
>> - int type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
>> -
>> - set_pte_range(vmf, folio, page, 1, vmf->address);
>> - add_mm_counter(vma->vm_mm, type, 1);
>> - ret = 0;
>> - } else {
>> - update_mmu_tlb(vma, vmf->address, vmf->pte);
>> + if (nr_pages == 1 && unlikely(vmf_pte_changed(vmf))) {
>> + update_mmu_tlb(vma, addr, vmf->pte);
>> + ret = VM_FAULT_NOPAGE;
>> + goto unlock;
>> + } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
>> + update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
>> ret = VM_FAULT_NOPAGE;
>> + goto unlock;
>> }
>
> We may add a vmf_pte_range_changed(), but separate it.
>
> Some very small nits, up to you,
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Thanks for reviewing. If a new version is needed, then I will clean up
these coding style issues.
On 11 Jun 2024, at 6:11, Baolin Wang wrote: > Add large folio mapping establishment support for finish_fault() as a > preparation, to support multi-size THP allocation of anonymous shmem pages > in the following patches. > > Keep the same behavior (per-page fault) for non-anon shmem to avoid inflating > the RSS unintentionally, and we can discuss what size of mapping to build > when extending mTHP to control non-anon shmem in the future. > > Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> > --- > mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 47 insertions(+), 10 deletions(-) > LGTM. Reviewed-by: Zi Yan <ziy@nvidia.com> -- Best Regards, Yan, Zi
On 2024/6/11 22:38, Zi Yan wrote: > On 11 Jun 2024, at 6:11, Baolin Wang wrote: > >> Add large folio mapping establishment support for finish_fault() as a >> preparation, to support multi-size THP allocation of anonymous shmem pages >> in the following patches. >> >> Keep the same behavior (per-page fault) for non-anon shmem to avoid inflating >> the RSS unintentionally, and we can discuss what size of mapping to build >> when extending mTHP to control non-anon shmem in the future. >> >> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++---------- >> 1 file changed, 47 insertions(+), 10 deletions(-) >> > LGTM. Reviewed-by: Zi Yan <ziy@nvidia.com> Thanks Zi for reviewing.
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