[PATCH v4 3/3] mm, memcg: inline swap-related functions to improve disabled memcg config

[Suren Baghdasaryan]

Inline mem_cgroup_try_charge_swap, mem_cgroup_uncharge_swap and
cgroup_throttle_swaprate functions to perform mem_cgroup_disabled static
key check inline before calling the main body of the function. This
minimizes the memcg overhead in the pagefault and exit_mmap paths when
memcgs are disabled using cgroup_disable=memory command-line option.
This change results in ~1% overhead reduction when running PFT test [1]
comparing {CONFIG_MEMCG=n} against {CONFIG_MEMCG=y, cgroup_disable=memory}
configuration on an 8-core ARM64 Android device.

[1] https://lkml.org/lkml/2006/8/29/294 also used in mmtests suite

Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
---
 include/linux/swap.h | 26 +++++++++++++++++++++++---
 mm/memcontrol.c      | 14 ++++----------
 mm/swapfile.c        |  5 +----
 3 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 6f5a43251593..f30d26b0f71d 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -721,7 +721,13 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 #endif
 
 #if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
-extern void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask);
+extern void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask);
+static inline  void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
+{
+	if (mem_cgroup_disabled())
+		return;
+	__cgroup_throttle_swaprate(page, gfp_mask);
+}
 #else
 static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 {
@@ -730,8 +736,22 @@ static inline void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 
 #ifdef CONFIG_MEMCG_SWAP
 extern void mem_cgroup_swapout(struct page *page, swp_entry_t entry);
-extern int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
-extern void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
+extern int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry);
+static inline int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
+{
+	if (mem_cgroup_disabled())
+		return 0;
+	return __mem_cgroup_try_charge_swap(page, entry);
+}
+
+extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
+static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
+{
+	if (mem_cgroup_disabled())
+		return;
+	__mem_cgroup_uncharge_swap(entry, nr_pages);
+}
+
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 extern bool mem_cgroup_swap_full(struct page *page);
 #else
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6adf50acdbe2..b8aab1900995 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7234,7 +7234,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 }
 
 /**
- * mem_cgroup_try_charge_swap - try charging swap space for a page
+ * __mem_cgroup_try_charge_swap - try charging swap space for a page
  * @page: page being added to swap
  * @entry: swap entry to charge
  *
@@ -7242,16 +7242,13 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
  *
  * Returns 0 on success, -ENOMEM on failure.
  */
-int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 {
 	unsigned int nr_pages = thp_nr_pages(page);
 	struct page_counter *counter;
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
-	if (mem_cgroup_disabled())
-		return 0;
-
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		return 0;
 
@@ -7287,18 +7284,15 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
 }
 
 /**
- * mem_cgroup_uncharge_swap - uncharge swap space
+ * __mem_cgroup_uncharge_swap - uncharge swap space
  * @entry: swap entry to uncharge
  * @nr_pages: the amount of swap space to uncharge
  */
-void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
+void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
 {
 	struct mem_cgroup *memcg;
 	unsigned short id;
 
-	if (mem_cgroup_disabled())
-		return;
-
 	id = swap_cgroup_record(entry, 0, nr_pages);
 	rcu_read_lock();
 	memcg = mem_cgroup_from_id(id);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 707fa0481bb4..04a0c83f1313 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3773,14 +3773,11 @@ static void free_swap_count_continuations(struct swap_info_struct *si)
 }
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
-void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
+void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 {
 	struct swap_info_struct *si, *next;
 	int nid = page_to_nid(page);
 
-	if (mem_cgroup_disabled())
-		return;
-
 	if (!(gfp_mask & __GFP_IO))
 		return;
 
-- 
2.32.0.93.g670b81a890-goog