patches/old/memcg-vmalloc-simplify-memcg_vmalloc-updates.patch

From: Shakeel Butt <shakeel.butt@linux.dev>
Subject: memcg: vmalloc: simplify MEMCG_VMALLOC updates
Date: Wed, 2 Apr 2025 22:33:26 -0700

The vmalloc region can either be charged to a single memcg or none.  At
the moment kernel traverses all the pages backing the vmalloc region to
update the MEMCG_VMALLOC stat.  However there is no need to look at all
the pages as all those pages will be charged to a single memcg or none. 
Simplify the MEMCG_VMALLOC update by just looking at the first page of the
vmalloc region.

[shakeel.butt@linux.dev: add comment]
  Link: https://lkml.kernel.org/r/bmlkdbqgwboyqrnxyom7n52fjmo76ux77jhqw5odc6c6dfon3h@zdylwtmlywbt
Link: https://lkml.kernel.org/r/20250403053326.26860-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmalloc.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/mm/vmalloc.c~memcg-vmalloc-simplify-memcg_vmalloc-updates
+++ a/mm/vmalloc.c
@@ -3371,12 +3371,13 @@ void vfree(const void *addr)
 
 	if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
 		vm_reset_perms(vm);
+	/* All pages of vm should be charged to same memcg, so use first one. */
+	if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES))
+		mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages);
 	for (i = 0; i < vm->nr_pages; i++) {
 		struct page *page = vm->pages[i];
 
 		BUG_ON(!page);
-		if (!(vm->flags & VM_MAP_PUT_PAGES))
-			mod_memcg_page_state(page, MEMCG_VMALLOC, -1);
 		/*
 		 * High-order allocs for huge vmallocs are split, so
 		 * can be freed as an array of order-0 allocations
@@ -3672,12 +3673,10 @@ static void *__vmalloc_area_node(struct
 		node, page_order, nr_small_pages, area->pages);
 
 	atomic_long_add(area->nr_pages, &nr_vmalloc_pages);
-	if (gfp_mask & __GFP_ACCOUNT) {
-		int i;
-
-		for (i = 0; i < area->nr_pages; i++)
-			mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC, 1);
-	}
+	/* All pages of vm should be charged to same memcg, so use first one. */
+	if (gfp_mask & __GFP_ACCOUNT && area->nr_pages)
+		mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC,
+				     area->nr_pages);
 
 	/*
 	 * If not enough pages were obtained to accomplish an
_