linux-kernel - Re: [patch] export percpu cpuacct cgroup stats

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Message-ID: <20081208143352.GG14856@elte.hu>
Date:	Mon, 8 Dec 2008 15:33:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ken Chen <kenchen@...gle.com>, Li Zefan <lizf@...fujitsu.com>,
	Paul Menage <menage@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch] export percpu cpuacct cgroup stats


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 5 Dec 2008 10:16:30 -0800 Ken Chen <kenchen@...gle.com> wrote:
> 
> > +static int cpuacct_percpu_seq_read(struct cgroup *cgroup, struct cftype *cft,
> > +				   struct seq_file *m)
> > +{
> > +	struct cpuacct *ca = cgroup_ca(cgroup);
> > +	u64 percpu;
> > +	int i;
> > +
> > +	for_each_possible_cpu(i) {
> > +		spin_lock_irq(&cpu_rq(i)->lock);
> > +		percpu = *percpu_ptr(ca->cpuusage, i);
> > +		spin_unlock_irq(&cpu_rq(i)->lock);
> > +		seq_printf(m, "%llu ", (unsigned long long) percpu);
> > +	}
> > +	seq_printf(m, "\n");
> > +	return 0;
> > +}
> 
> The locking is only needed for 32-bit, I assume?
> 
> The iteration across all possible CPUs seems a bit lame - that code
> looks pretty easy to convert to hotplug goodness.
> 
> (All of which pertains to existing code, not to this patch).

fair enough. Ken, would you mind updating it in this fashion?

	Ingo
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