[PATCH v3 4/4] mm/madvise: batch tlb flushes for MADV_DONTNEED[_LOCKED]

[SeongJae Park]

MADV_DONTNEED[_LOCKED] handling for [process_]madvise() flushes tlb for
each vma of each address range.  Update the logic to do tlb flushes in a
batched way.  Initialize an mmu_gather object from do_madvise() and
vector_madvise(), which are the entry level functions for
[process_]madvise(), respectively.  And pass those objects to the
function for per-vma work, via madvise_behavior struct.  Make the
per-vma logic not flushes tlb on their own but just saves the tlb
entries to the received mmu_gather object.  For this internal logic
change, make zap_page_range_single_batched() non-static and use it
directly from madvise_dontneed_single_vma().  Finally, the entry level
functions flush the tlb entries that gathered for the entire user
request, at once.

Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 mm/internal.h |  3 +++
 mm/madvise.c  | 11 ++++++++---
 mm/memory.c   |  4 ++--
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index ef92e88738fe..c5f9dd007215 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -435,6 +435,9 @@ void unmap_page_range(struct mmu_gather *tlb,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end,
 			     struct zap_details *details);
+void zap_page_range_single_batched(struct mmu_gather *tlb,
+		struct vm_area_struct *vma, unsigned long addr,
+		unsigned long size, struct zap_details *details);
 int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
 			   gfp_t gfp);
 
diff --git a/mm/madvise.c b/mm/madvise.c
index 951038a9f36f..8433ac9b27e0 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -851,7 +851,8 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
  * An interface that causes the system to free clean pages and flush
  * dirty pages is already available as msync(MS_INVALIDATE).
  */
-static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
+static long madvise_dontneed_single_vma(struct madvise_behavior *madv_behavior,
+					struct vm_area_struct *vma,
 					unsigned long start, unsigned long end)
 {
 	struct zap_details details = {
@@ -859,7 +860,8 @@ static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 		.even_cows = true,
 	};
 
-	zap_page_range_single(vma, start, end - start, &details);
+	zap_page_range_single_batched(
+			madv_behavior->tlb, vma, start, end - start, &details);
 	return 0;
 }
 
@@ -950,7 +952,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
 	}
 
 	if (behavior == MADV_DONTNEED || behavior == MADV_DONTNEED_LOCKED)
-		return madvise_dontneed_single_vma(vma, start, end);
+		return madvise_dontneed_single_vma(
+				madv_behavior, vma, start, end);
 	else if (behavior == MADV_FREE)
 		return madvise_free_single_vma(madv_behavior, vma, start, end);
 	else
@@ -1628,6 +1631,8 @@ static void madvise_unlock(struct mm_struct *mm, int behavior)
 static bool madvise_batch_tlb_flush(int behavior)
 {
 	switch (behavior) {
+	case MADV_DONTNEED:
+	case MADV_DONTNEED_LOCKED:
 	case MADV_FREE:
 		return true;
 	default:
diff --git a/mm/memory.c b/mm/memory.c
index 690695643dfb..559f3e194438 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1998,7 +1998,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
 	mmu_notifier_invalidate_range_end(&range);
 }
 
-/*
+/**
  * zap_page_range_single_batched - remove user pages in a given range
  * @tlb: pointer to the caller's struct mmu_gather
  * @vma: vm_area_struct holding the applicable pages
@@ -2009,7 +2009,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
  * @tlb shouldn't be NULL.  The range must fit into one VMA.  If @vma is for
  * hugetlb, @tlb is flushed and re-initialized by this function.
  */
-static void zap_page_range_single_batched(struct mmu_gather *tlb,
+void zap_page_range_single_batched(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long address,
 		unsigned long size, struct zap_details *details)
 {
-- 
2.39.5