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

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Message-ID: <20090227063955.GS11421@balbir.in.ibm.com>
Date:	Fri, 27 Feb 2009 12:09:55 +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 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.
-- 
	Balbir
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