linux-kernel - Re: Re: Re: [PATCH 1/3] cgroup/rstat: Fix forceidle time in cpu.stat

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Message-ID: <5b71f446-8a83-46e1-9e28-fb5f90f78793@bytedance.com>
Date: Sat, 25 Jan 2025 12:54:42 +0800
From: Abel Wu <wuyun.abel@...edance.com>
To: Tejun Heo <tj@...nel.org>
Cc: chenridong <chenridong@...wei.com>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>,
 Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 Thomas Gleixner <tglx@...utronix.de>, Yury Norov <yury.norov@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Bitao Hu
 <yaoma@...ux.alibaba.com>,
 "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: Re: Re: [PATCH 1/3] cgroup/rstat: Fix forceidle time in cpu.stat

On 1/25/25 7:49 AM, Tejun Heo Wrote:
> On Fri, Jan 24, 2025 at 03:49:16PM +0800, Abel Wu wrote:
> ...
>>>> --- a/kernel/cgroup/rstat.c
>>>> +++ b/kernel/cgroup/rstat.c
>>>> @@ -613,36 +613,33 @@ static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat
>>>>    void cgroup_base_stat_cputime_show(struct seq_file *seq)
>>>>    {
>>>>    	struct cgroup *cgrp = seq_css(seq)->cgroup;
>>>> -	u64 usage, utime, stime, ntime;
>>>> +	struct cgroup_base_stat bstat;
>>>>    	if (cgroup_parent(cgrp)) {
>>>>    		cgroup_rstat_flush_hold(cgrp);
>>>> -		usage = cgrp->bstat.cputime.sum_exec_runtime;
>>>> +		bstat = cgrp->bstat;
>>>
>>> Thank you for finding that.
>>> In my version 2, I used to assign cgrp->bstat to bstat.
>>> This is Tj's comment:
>>> https://lore.kernel.org/linux-kernel/ZoQ2ti7nnz9EJSc3@slm.duckdns.org/
> 
> I wasn't saying that memcpy() should be used instead of assignment. I was
> saying that if a non-trivial struct can be pointed to instead of being
> copied, it should be pointed to. If all the fields need to be snapshotted,
> assigning is fine.

Thanks for your clarification, Tejun. I will post v2 to address Michal's
comments.

Best Regards,
	Abel