sched/cpuacct: Simplify the cpuacct code

 - Use for() instead of while() loop in some functions
   to make the code simpler.

 - Use this_cpu_ptr() instead of per_cpu_ptr() to make the code
   cleaner and a bit faster.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d8a7ef9592f55224630cb26dea239f05b6398a4e.1458187654.git.zhaolei@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 9c2bbf7..434c2fa 100644 (file)
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -238,23 +238,10 @@ static struct cftype files[] = {
 void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 {
        struct cpuacct *ca;
-       int cpu;
-
-       cpu = task_cpu(tsk);
 
        rcu_read_lock();
-
-       ca = task_ca(tsk);
-
-       while (true) {
-               u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
-               *cpuusage += cputime;
-
-               ca = parent_ca(ca);
-               if (!ca)
-                       break;
-       }
-
+       for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
+               *this_cpu_ptr(ca->cpuusage) += cputime;
        rcu_read_unlock();
 }
 
@@ -263,18 +250,13 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
  *
  * Note: it's the caller that updates the account of the root cgroup.
  */
-void cpuacct_account_field(struct task_struct *p, int index, u64 val)
+void cpuacct_account_field(struct task_struct *tsk, int index, u64 val)
 {
-       struct kernel_cpustat *kcpustat;
        struct cpuacct *ca;
 
        rcu_read_lock();
-       ca = task_ca(p);
-       while (ca != &root_cpuacct) {
-               kcpustat = this_cpu_ptr(ca->cpustat);
-               kcpustat->cpustat[index] += val;
-               ca = parent_ca(ca);
-       }
+       for (ca = task_ca(tsk); ca != &root_cpuacct; ca = parent_ca(ca))
+               this_cpu_ptr(ca->cpustat)->cpustat[index] += val;
        rcu_read_unlock();
 }
 

diff --git a/kernel/sched/cpuacct.h b/kernel/sched/cpuacct.h
index ed60562..ba72807 100644 (file)
--- a/kernel/sched/cpuacct.h
+++ b/kernel/sched/cpuacct.h
@@ -1,7 +1,7 @@
 #ifdef CONFIG_CGROUP_CPUACCT
 
 extern void cpuacct_charge(struct task_struct *tsk, u64 cputime);
-extern void cpuacct_account_field(struct task_struct *p, int index, u64 val);
+extern void cpuacct_account_field(struct task_struct *tsk, int index, u64 val);
 
 #else
 
@@ -10,7 +10,7 @@ static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 }
 
 static inline void
-cpuacct_account_field(struct task_struct *p, int index, u64 val)
+cpuacct_account_field(struct task_struct *tsk, int index, u64 val)
 {
 }