1 files changed, 19 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f96be9370b75..bae6fcfe6d75 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8998,12 +8998,30 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 }
 
 /*
+ * When CONFIG_VIRT_CPU_ACCOUNTING is enabled one jiffy can be very large
+ * in cputime_t units. As a result, cpuacct_update_stats calls
+ * percpu_counter_add with values large enough to always overflow the
+ * per cpu batch limit causing bad SMP scalability.
+ *
+ * To fix this we scale percpu_counter_batch by cputime_one_jiffy so we
+ * batch the same amount of time with CONFIG_VIRT_CPU_ACCOUNTING disabled
+ * and enabled. We cap it at INT_MAX which is the largest allowed batch value.
+ */
+#ifdef CONFIG_SMP
+#define CPUACCT_BATCH   \
+        min_t(long, percpu_counter_batch * cputime_one_jiffy, INT_MAX)
+#else
+#define CPUACCT_BATCH   0
+#endif
+
+/*
  * Charge the system/user time to the task's accounting group.
  */
 static void cpuacct_update_stats(struct task_struct *tsk,
                 enum cpuacct_stat_index idx, cputime_t val)
 {
         struct cpuacct *ca;
+        int batch = CPUACCT_BATCH;
 
         if (unlikely(!cpuacct_subsys.active))
                 return;
@@ -9012,7 +9030,7 @@ static void cpuacct_update_stats(struct task_struct *tsk,
         ca = task_ca(tsk);
 
         do {
-                percpu_counter_add(&ca->cpustat[idx], val);
+                __percpu_counter_add(&ca->cpustat[idx], val, batch);
                 ca = ca->parent;
         } while (ca);
         rcu_read_unlock();