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sched/cpuacct: Optimize away RCU read lock 

Since cpuacct_charge() is called from the scheduler update_curr(),
we must already have rq lock held, then the RCU read lock can
be optimized away.

And do the same thing in it's wrapper cgroup_account_cputime(),
but we can't use lockdep_assert_rq_held() there, which defined
in kernel/sched/sched.h.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220220051426.5274-2-zhouchengming@bytedance.com
This commit is contained in:
Chengming Zhou 2022-02-20 13:14:25 +08:00 committed by Peter Zijlstra
parent 248cc9993d
commit dc6e0818bc
2 changed files with 1 additions and 5 deletions
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2
include/linux/cgroup.h
View File

@ -791,11 +791,9 @@ static inline void cgroup_account_cputime(struct task_struct *task,
cpuacct_charge(task, delta_exec);
rcu_read_lock();
cgrp = task_dfl_cgroup(task);
if (cgroup_parent(cgrp))
__cgroup_account_cputime(cgrp, delta_exec);
rcu_read_unlock();
}
static inline void cgroup_account_cputime_field(struct task_struct *task,

4
kernel/sched/cpuacct.c
View File

@ -337,12 +337,10 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
unsigned int cpu = task_cpu(tsk);
struct cpuacct *ca;
rcu_read_lock();
lockdep_assert_rq_held(cpu_rq(cpu));
for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
*per_cpu_ptr(ca->cpuusage, cpu) += cputime;
rcu_read_unlock();
}
/*