linux-kernel - [PATCH v2 1/3] mm: avoid extra mem_alloc_profiling

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Message-ID: <20250201231803.2661189-1-surenb@google.com>
Date: Sat,  1 Feb 2025 15:18:00 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, vbabka@...e.cz, rostedt@...dmis.org, 
	peterz@...radead.org, yuzhao@...gle.com, minchan@...gle.com, 
	shakeel.butt@...ux.dev, souravpanda@...gle.com, pasha.tatashin@...een.com, 
	00107082@....com, quic_zhenhuah@...cinc.com, surenb@...gle.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] mm: avoid extra mem_alloc_profiling_enabled() checks

Refactor code to avoid extra mem_alloc_profiling_enabled() checks inside
pgalloc_tag_get() function which is often called after that check was
already done.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 include/linux/pgalloc_tag.h | 35 +++++++++++++++++++----------------
 lib/alloc_tag.c             |  6 +++---
 mm/page_alloc.c             |  3 +--
 3 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
index 3469c4b20105..4a82b6b4820e 100644
--- a/include/linux/pgalloc_tag.h
+++ b/include/linux/pgalloc_tag.h
@@ -205,28 +205,32 @@ static inline void pgalloc_tag_sub(struct page *page, unsigned int nr)
 	}
 }
 
-static inline struct alloc_tag *pgalloc_tag_get(struct page *page)
+/* Should be called only if mem_alloc_profiling_enabled() */
+static inline struct alloc_tag *__pgalloc_tag_get(struct page *page)
 {
 	struct alloc_tag *tag = NULL;
-
-	if (mem_alloc_profiling_enabled()) {
-		union pgtag_ref_handle handle;
-		union codetag_ref ref;
-
-		if (get_page_tag_ref(page, &ref, &handle)) {
-			alloc_tag_sub_check(&ref);
-			if (ref.ct)
-				tag = ct_to_alloc_tag(ref.ct);
-			put_page_tag_ref(handle);
-		}
+	union pgtag_ref_handle handle;
+	union codetag_ref ref;
+
+	if (get_page_tag_ref(page, &ref, &handle)) {
+		alloc_tag_sub_check(&ref);
+		if (ref.ct)
+			tag = ct_to_alloc_tag(ref.ct);
+		put_page_tag_ref(handle);
 	}
 
 	return tag;
 }
 
-static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr)
+static inline void pgalloc_tag_sub_pages(struct page *page, unsigned int nr)
 {
-	if (mem_alloc_profiling_enabled() && tag)
+	struct alloc_tag *tag;
+
+	if (!mem_alloc_profiling_enabled())
+		return;
+
+	tag = __pgalloc_tag_get(page);
+	if (tag)
 		this_cpu_sub(tag->counters->bytes, PAGE_SIZE * nr);
 }
 
@@ -241,8 +245,7 @@ static inline void clear_page_tag_ref(struct page *page) {}
 static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
 				   unsigned int nr) {}
 static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) {}
-static inline struct alloc_tag *pgalloc_tag_get(struct page *page) { return NULL; }
-static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr) {}
+static inline void pgalloc_tag_sub_pages(struct page *page, unsigned int nr) {}
 static inline void alloc_tag_sec_init(void) {}
 static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new_order) {}
 static inline void pgalloc_tag_swap(struct folio *new, struct folio *old) {}
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 19b45617bdcf..1d893e313614 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -174,7 +174,7 @@ void pgalloc_tag_split(struct folio *folio, int old_order, int new_order)
 	if (!mem_alloc_profiling_enabled())
 		return;
 
-	tag = pgalloc_tag_get(&folio->page);
+	tag = __pgalloc_tag_get(&folio->page);
 	if (!tag)
 		return;
 
@@ -200,10 +200,10 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
 	if (!mem_alloc_profiling_enabled())
 		return;
 
-	tag_old = pgalloc_tag_get(&old->page);
+	tag_old = __pgalloc_tag_get(&old->page);
 	if (!tag_old)
 		return;
-	tag_new = pgalloc_tag_get(&new->page);
+	tag_new = __pgalloc_tag_get(&new->page);
 	if (!tag_new)
 		return;
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 579789600a3c..b7e3b45183ed 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4832,12 +4832,11 @@ void __free_pages(struct page *page, unsigned int order)
 {
 	/* get PageHead before we drop reference */
 	int head = PageHead(page);
-	struct alloc_tag *tag = pgalloc_tag_get(page);
 
 	if (put_page_testzero(page))
 		free_frozen_pages(page, order);
 	else if (!head) {
-		pgalloc_tag_sub_pages(tag, (1 << order) - 1);
+		pgalloc_tag_sub_pages(page, (1 << order) - 1);
 		while (order-- > 0)
 			free_frozen_pages(page + (1 << order), order);
 	}

base-commit: 7de6fd8ab65003f050aa58e705592745717ed318
-- 
2.48.1.362.g079036d154-goog