linux-kernel - Re: [PATCH] change cpuacct usage percpu format

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Message-ID: <20090227070148.GU11421@balbir.in.ibm.com>
Date:	Fri, 27 Feb 2009 12:31:48 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kenchen@...gle.com, "menage@...gle.com" <menage@...gle.com>,
	"lizf@...fujitsu.com" <lizf@...fujitsu.com>, mingo@...e.hu,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] change cpuacct usage percpu format

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-02-27 15:55:17]:

> On Fri, 27 Feb 2009 12:09:55 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-02-27 14:05:37]:
> > 
> > > I'd like to change cpuacct.usage_percpu format before it's widely used.
> > > Current format is not easy to use in hardware with DR feature.
> > > 
> > > ==
> > > cpuacct.usage_percpu shows per cpu usage information via cgroupfs.
> > > It shows all present cpus information and "whose information ?"
> > > is explained just by index of data implicitly.
> > > 
> > > IIRC, there is physical cpu hotplug and it can remove
> > > cpus and change present map. Considering a software which records
> > > this information pediodically(like sar.), its better to show id of cpu
> > > in explict way.
> > > 
> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > > ---
> > >  kernel/sched.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > Index: mmotm-2.6.29-Feb24/kernel/sched.c
> > > ===================================================================
> > > --- mmotm-2.6.29-Feb24.orig/kernel/sched.c
> > > +++ mmotm-2.6.29-Feb24/kernel/sched.c
> > > @@ -9719,7 +9719,7 @@ static int cpuacct_percpu_seq_read(struc
> > > 
> > >  	for_each_present_cpu(i) {
> > >  		percpu = cpuacct_cpuusage_read(ca, i);
> > > -		seq_printf(m, "%llu ", (unsigned long long) percpu);
> > > +		seq_printf(m, "%d %llu\n", i, (unsigned long long) percpu);
> > 
> > Seems like a reasonable change, but I wonder if " " should the
> > separator between the CPU and data, I wounder if we should use
> > cpu:usage_per_cpu.
> 
> Ah, no strong reason for " ". 
> 
> Hmm, like this ?
> ==
> seq_printf(m, "%d: %llu\n", i, (unsigned long long) percpu);
> or
> seq_printf(m, "%d\t: %llu\n", i, (unsigned long long) percpu);
> ==
> 
>

I'd like to see : and not space after it so something like

seq_printf(m, "%d:%llu\n", i, (unsigned long long) percpu);
-- 
	Balbir
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