Re: [PATCH v2 4/5] mm/memcg: Separate out object stock data into its own struct

[Shakeel Butt]

On Mon, Apr 12, 2021 at 3:55 PM Waiman Long  wrote:
>
> The object stock data stored in struct memcg_stock_pcp are independent
> of the other page based data stored there. Separating them out into
> their own struct to highlight the independency.
>
> Signed-off-by: Waiman Long 
> Acked-by: Roman Gushchin 

Reviewed-by: Shakeel Butt 

[PATCH v2 4/5] mm/memcg: Separate out object stock data into its own struct

[Waiman Long]

The object stock data stored in struct memcg_stock_pcp are independent
of the other page based data stored there. Separating them out into
their own struct to highlight the independency.

Signed-off-by: Waiman Long 
Acked-by: Roman Gushchin 
---
 mm/memcontrol.c | 41 ++---
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 539c3b632e47..69f728383efe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2214,17 +2214,22 @@ void unlock_page_memcg(struct page *page)
 }
 EXPORT_SYMBOL(unlock_page_memcg);
 
-struct memcg_stock_pcp {
-   struct mem_cgroup *cached; /* this never be root cgroup */
-   unsigned int nr_pages;
-
+struct obj_stock {
 #ifdef CONFIG_MEMCG_KMEM
struct obj_cgroup *cached_objcg;
struct pglist_data *cached_pgdat;
unsigned int nr_bytes;
int vmstat_idx;
int vmstat_bytes;
+#else
+   int dummy[0];
 #endif
+};
+
+struct memcg_stock_pcp {
+   struct mem_cgroup *cached; /* this never be root cgroup */
+   unsigned int nr_pages;
+   struct obj_stock obj;
 
struct work_struct work;
unsigned long flags;
@@ -2234,12 +2239,12 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, 
memcg_stock);
 static DEFINE_MUTEX(percpu_charge_mutex);
 
 #ifdef CONFIG_MEMCG_KMEM
-static void drain_obj_stock(struct memcg_stock_pcp *stock);
+static void drain_obj_stock(struct obj_stock *stock);
 static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
 struct mem_cgroup *root_memcg);
 
 #else
-static inline void drain_obj_stock(struct memcg_stock_pcp *stock)
+static inline void drain_obj_stock(struct obj_stock *stock)
 {
 }
 static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
@@ -2249,6 +2254,13 @@ static bool obj_stock_flush_required(struct 
memcg_stock_pcp *stock,
 }
 #endif
 
+static inline struct obj_stock *current_obj_stock(void)
+{
+   struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock);
+
+   return &stock->obj;
+}
+
 /**
  * consume_stock: Try to consume stocked charge on this cpu.
  * @memcg: memcg to consume from.
@@ -2315,7 +2327,7 @@ static void drain_local_stock(struct work_struct *dummy)
local_irq_save(flags);
 
stock = this_cpu_ptr(&memcg_stock);
-   drain_obj_stock(stock);
+   drain_obj_stock(&stock->obj);
drain_stock(stock);
clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
 
@@ -3177,13 +3189,13 @@ static inline void mod_objcg_state(struct obj_cgroup 
*objcg,
 
 static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
 {
-   struct memcg_stock_pcp *stock;
+   struct obj_stock *stock;
unsigned long flags;
bool ret = false;
 
local_irq_save(flags);
 
-   stock = this_cpu_ptr(&memcg_stock);
+   stock = current_obj_stock();
if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) {
stock->nr_bytes -= nr_bytes;
ret = true;
@@ -3194,7 +3206,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, 
unsigned int nr_bytes)
return ret;
 }
 
-static void drain_obj_stock(struct memcg_stock_pcp *stock)
+static void drain_obj_stock(struct obj_stock *stock)
 {
struct obj_cgroup *old = stock->cached_objcg;
 
@@ -3242,8 +3254,8 @@ static bool obj_stock_flush_required(struct 
memcg_stock_pcp *stock,
 {
struct mem_cgroup *memcg;
 
-   if (stock->cached_objcg) {
-   memcg = obj_cgroup_memcg(stock->cached_objcg);
+   if (stock->obj.cached_objcg) {
+   memcg = obj_cgroup_memcg(stock->obj.cached_objcg);
if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
return true;
}
@@ -3253,9 +3265,8 @@ static bool obj_stock_flush_required(struct 
memcg_stock_pcp *stock,
 
 static void __refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
 {
-   struct memcg_stock_pcp *stock;
+   struct obj_stock *stock = current_obj_stock();
 
-   stock = this_cpu_ptr(&memcg_stock);
if (stock->cached_objcg != objcg) { /* reset if necessary */
drain_obj_stock(stock);
obj_cgroup_get(objcg);
@@ -3280,7 +3291,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, 
unsigned int nr_bytes)
 static void __mod_obj_stock_state(struct obj_cgroup *objcg,
  struct pglist_data *pgdat, int idx, int nr)
 {
-   struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock);
+   struct obj_stock *stock = current_obj_stock();
 
if (stock->cached_objcg != objcg) {
/* Output the current data as is */
-- 
2.18.1