linux-kernel - Re: [RFC PATCH] cpuacct: per-cgroup utime/stime statistics

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Date:	Wed, 11 Mar 2009 14:24:58 +0530
From:	Bharata B Rao <bharata@...ux.vnet.ibm.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, Balaji Rao <balajirrao@...il.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Paul Menage <menage@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC PATCH] cpuacct: per-cgroup utime/stime statistics - v1

On Wed, Mar 11, 2009 at 09:15:48AM +0800, Li Zefan wrote:
> > +static const struct cpuacct_stat_desc {
> > +	const char *msg;
> > +	u64 unit;
> > +} cpuacct_stat_desc[] = {
> > +	[CPUACCT_STAT_UTIME] = { "utime", 1, },
> > +	[CPUACCT_STAT_STIME] = { "stime", 1, },
> > +};
> > +
> 
> I think we can just remove 'unit'.

Ok, they are redundant. Will do.

> 
> > +static int cpuacct_stats_show(struct cgroup *cgrp, struct cftype *cft,
> > +		struct cgroup_map_cb *cb)
> > +{
> > +	struct cpuacct *ca = cgroup_ca(cgrp);
> > +	int i;
> > +
> > +	for (i = 0; i < CPUACCT_STAT_NSTATS; i++) {
> > +		s64 val = percpu_counter_read(&ca->cpustat[i]);
> > +		val *= cpuacct_stat_desc[i].unit;
> > +		cb->fill(cb, cpuacct_stat_desc[i].msg, val);
> > +	}
> > +	return 0;
> > +}
> > +
> ...
> > +/*
> > + * Account the system/user time to the task's accounting group.
> > + */
> > +static void cpuacct_update_stats(struct task_struct *tsk,
> > +		enum cpuacct_stat_index idx, int val)
> > +{
> > +	struct cpuacct *ca;
> > +
> > +	if (!cpuacct_subsys.active)
> 
> if (unlikely(!cpuacct_subsys.active)))

Ok.

> 
> > +		return;
> > +
> > +	ca = task_ca(tsk);
> > +
> > +	for (; ca; ca = ca->parent)
> > +		percpu_counter_add(&ca->cpustat[idx], val);
> > +}
> > +
> 
> We can reduce one NULL check:
> 
> do (
> 	percpu_counter_add();
> 	ca = ca->parent;
> } while (ca);

Sure. Will address all these in the next iteration.

Regards,
Bharata.
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