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Date:   Wed, 18 Aug 2021 11:33:39 -0400
From:   Daniel Jordan <daniel.m.jordan@oracle.com>
To:     "Li,Rongqing" <lirongqing@baidu.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
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        "songmuchun@bytedance.com" <songmuchun@bytedance.com>,
        Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>
Subject: Re: =?utf-8?B?562U5aSNOiDnrZTlpI0=?= =?utf-8?Q?=3A?= [PATCH][RFC]
 sched/cpuacct: Fix cpuacct charge
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On Tue, Aug 17, 2021 at 03:55:08AM +0000, Li,Rongqing wrote:
> > > 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

I'll leave that to someone else, got other things going on for now.