[v6,8/8] hugetlb: batch TLB flushes when restoring vmemmap

Commit Message

Mike Kravetz Sept. 25, 2023, 11:48 p.m. UTC

Update the internal hugetlb restore vmemmap code path such that TLB
flushing can be batched.  Use the existing mechanism of passing the
VMEMMAP_REMAP_NO_TLB_FLUSH flag to indicate flushing should not be
performed for individual pages.  The routine hugetlb_vmemmap_restore_folios
is the only user of this new mechanism, and it will perform a global
flush after all vmemmap is restored.

Signed-off-by: Joao Martins <[e-mail]>
Signed-off-by: Mike Kravetz <[e-mail]>
---
 mm/hugetlb_vmemmap.c | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

Comments

Muchun Song Sept. 26, 2023, 2:20 a.m. UTC | #1

> On Sep 26, 2023, at 07:48, Mike Kravetz <[e-mail]> wrote:
> 
> Update the internal hugetlb restore vmemmap code path such that TLB
> flushing can be batched.  Use the existing mechanism of passing the
> VMEMMAP_REMAP_NO_TLB_FLUSH flag to indicate flushing should not be
> performed for individual pages.  The routine hugetlb_vmemmap_restore_folios
> is the only user of this new mechanism, and it will perform a global
> flush after all vmemmap is restored.
> 
> Signed-off-by: Joao Martins <[e-mail]>
> Signed-off-by: Mike Kravetz <[e-mail]>

Reviewed-by: Muchun Song <[e-mail]>

Thanks.

Patch

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 9df350372046..d2999c303031 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -461,18 +461,19 @@  static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
  * @end:	end address of the vmemmap virtual address range that we want to
  *		remap.
  * @reuse:	reuse address.
+ * @flags:	modifications to vmemmap_remap_walk flags
  *
  * Return: %0 on success, negative error code otherwise.
  */
 static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
-			       unsigned long reuse)
+			       unsigned long reuse, unsigned long flags)
 {
 	LIST_HEAD(vmemmap_pages);
 	struct vmemmap_remap_walk walk = {
 		.remap_pte	= vmemmap_restore_pte,
 		.reuse_addr	= reuse,
 		.vmemmap_pages	= &vmemmap_pages,
-		.flags		= 0,
+		.flags		= flags,
 	};
 
 	/* See the comment in the vmemmap_remap_free(). */
@@ -494,17 +495,7 @@  EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
 static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
 core_param(hugetlb_free_vmemmap, vmemmap_optimize_enabled, bool, 0);
 
-/**
- * hugetlb_vmemmap_restore - restore previously optimized (by
- *			     hugetlb_vmemmap_optimize()) vmemmap pages which
- *			     will be reallocated and remapped.
- * @h:		struct hstate.
- * @head:	the head page whose vmemmap pages will be restored.
- *
- * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
- * negative error code otherwise.
- */
-int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
+static int __hugetlb_vmemmap_restore(const struct hstate *h, struct page *head, unsigned long flags)
 {
 	int ret;
 	unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
@@ -525,7 +516,7 @@  int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
 	 * When a HugeTLB page is freed to the buddy allocator, previously
 	 * discarded vmemmap pages must be allocated and remapping.
 	 */
-	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse);
+	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse, flags);
 	if (!ret) {
 		ClearHPageVmemmapOptimized(head);
 		static_branch_dec(&hugetlb_optimize_vmemmap_key);
@@ -534,6 +525,21 @@  int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
 	return ret;
 }
 
+/**
+ * hugetlb_vmemmap_restore - restore previously optimized (by
+ *				hugetlb_vmemmap_optimize()) vmemmap pages which
+ *				will be reallocated and remapped.
+ * @h:		struct hstate.
+ * @head:	the head page whose vmemmap pages will be restored.
+ *
+ * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
+ * negative error code otherwise.
+ */
+int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
+{
+	return __hugetlb_vmemmap_restore(h, head, 0);
+}
+
 /**
  * hugetlb_vmemmap_restore_folios - restore vmemmap for every folio on the list.
  * @h:			hstate.
@@ -557,7 +563,8 @@  long hugetlb_vmemmap_restore_folios(const struct hstate *h,
 
 	list_for_each_entry_safe(folio, t_folio, folio_list, lru) {
 		if (folio_test_hugetlb_vmemmap_optimized(folio)) {
-			ret = hugetlb_vmemmap_restore(h, &folio->page);
+			ret = __hugetlb_vmemmap_restore(h, &folio->page,
+						VMEMMAP_REMAP_NO_TLB_FLUSH);
 			if (ret)
 				break;
 			restored++;
@@ -567,6 +574,8 @@  long hugetlb_vmemmap_restore_folios(const struct hstate *h,
 		list_move(&folio->lru, non_hvo_folios);
 	}
 
+	if (restored)
+		flush_tlb_all();
 	if (!ret)
 		ret = restored;
 	return ret;