linux-kernel - 答复: 答复: [PATCH][RFC] sched/cpuacct: Fix cpuacct charge

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Date:   Tue, 17 Aug 2021 03:55:08 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "bsegall@...gle.com" <bsegall@...gle.com>,
        "mgorman@...e.de" <mgorman@...e.de>,
        "bristot@...hat.co" <bristot@...hat.co>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "songmuchun@...edance.com" <songmuchun@...edance.com>,
        Michal Koutný <mkoutny@...e.com>
Subject: 答复: 答复: [PATCH][RFC] sched/cpuacct: Fix cpuacct charge

> > diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index
> > 893eece..48b117e 100644
> > --- a/kernel/sched/cpuacct.c
> > +++ b/kernel/sched/cpuacct.c
> > @@ -340,7 +340,12 @@ void cpuacct_charge(struct task_struct *tsk, u64
> > cputime)  {
> >         struct cpuacct *ca;
> >         int index = CPUACCT_STAT_SYSTEM;
> > -       struct pt_regs *regs = get_irq_regs() ? : task_pt_regs(tsk);
> > +       struct pt_regs *regs;
> > +
> > +       if (task_cpu(tsk) == raw_smp_processor_id())
> > +               regs = get_irq_regs() ? : task_pt_regs(tsk);
> > +       else
> > +               regs = task_pt_regs(tsk);
> >
> >         if (regs && user_mode(regs))
> >                 index = CPUACCT_STAT_USER;
> 
> It still suffers from task_pt_regs().
> 
> Why not make cpuacct use cgroup2's approach?  Remember only delta_exec
> here, then on reading cpuacct.usage_*, use cputime_adjust() to scale the
> user/sys from cpuacct_account_field().
> 

I think your suggestion is reasonable, Could you send a patch


> It's arguably more than just a fix for cgroup1, but there have been a few
> complaints about this function lately.
> 
> >         rcu_read_lock();
> >
> >         for (ca = task_ca(tsk); ca; ca = parent_ca(ca))
> >               __this_cpu_add(ca->cpuusage->usages[index], cputime);
> >
> >         rcu_read_unlock();
> 
> By the way, I think the __this_cpu_add() can be wrong in cases like you originally
> describe.  Seems like a bug in 73e6aafd9ea8 ("sched/cpuacct:
> Simplify the cpuacct code").

We find this issue too.

-Li