linux-kernel - Re: [PATCH v3 3/6] expose fine-grained per-cpu data for cpuacct stats

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Date:	Wed, 30 May 2012 12:43:48 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	devel@...nvz.org, Paul Turner <pjt@...gle.com>,
	Tejun Heo <tj@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, handai.szj@...il.com,
	Andrew.Phillips@...x.com, Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH v3 3/6] expose fine-grained per-cpu data for cpuacct
 stats

On Wed, 2012-05-30 at 14:34 +0400, Glauber Costa wrote:
> On 05/30/2012 02:34 PM, Peter Zijlstra wrote:
> > On Wed, 2012-05-30 at 13:48 +0400, Glauber Costa wrote:
> >
> >> +static int cpuacct_stats_percpu_show(struct cgroup *cgrp, struct cftype *cft,
> >> +				     struct cgroup_map_cb *cb)
> >> +{
> >> +	struct cpuacct *ca = cgroup_ca(cgrp);
> >> +	int cpu;
> >> +
> >> +	for_each_online_cpu(cpu) {
> >> +		do_fill_cb(cb, ca, "user", cpu, CPUTIME_USER);
> >> +		do_fill_cb(cb, ca, "nice", cpu, CPUTIME_NICE);
> >> +		do_fill_cb(cb, ca, "system", cpu, CPUTIME_SYSTEM);
> >> +		do_fill_cb(cb, ca, "irq", cpu, CPUTIME_IRQ);
> >> +		do_fill_cb(cb, ca, "softirq", cpu, CPUTIME_SOFTIRQ);
> >> +		do_fill_cb(cb, ca, "guest", cpu, CPUTIME_GUEST);
> >> +		do_fill_cb(cb, ca, "guest_nice", cpu, CPUTIME_GUEST_NICE);
> >> +	}
> >> +
> >> +	return 0;
> >> +}
> >
> > Uhm, hotplug anyone?
> What's with hotplug ?


Who's to say all cpus are online at this point? If you don't want to
make the files come and go with hotplug, one should use
for_each_possible_cpu().


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