[PATCH v3 2/3] Some small restruct for cpuacct

From: Zhao Lei
Date: Thu Mar 17 2016 - 00:22:35 EST


1: Use for() instead of while() loop in some functions
to make code simple.
2: Use this_cpu_ptr() instead of per_cpu_ptr() to make code
clean with little performance up.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
---
kernel/sched/cpuacct.c | 28 +++++-----------------------
kernel/sched/cpuacct.h | 4 ++--
2 files changed, 7 insertions(+), 25 deletions(-)

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 9c2bbf7..434c2fa 100644
--- 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
--- 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)
{
}

--
1.8.5.1