linux-kernel - Re: [patch 2/2] sched: allow cpuacct stats to be reset

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Date:	Fri, 7 Mar 2008 10:30:39 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc:	vatsa@...ux.vnet.ibm.com, menage@...gle.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	akpm@...ux-foundation.org, skumar@...ux.vnet.ibm.com
Subject: Re: [patch 2/2] sched: allow cpuacct stats to be reset

* Dhaval Giani <dhaval@...ux.vnet.ibm.com> [2008-02-29 10:02:44]:

> Currently the schedstats implementation does not allow the statistics
> to be reset. This patch aims to allow that.
> 
> echo 0 > cpuacct.usage
> 
> resets the usage. Any other value is not allowed and returns -EINVAL.
> 
> Signed-off-by: Dhaval Giani <dhaval@...ux.vnet.ibm.com>
> 
> ---
>  kernel/sched.c |   24 ++++++++++++++++++++++++
>  1 files changed, 24 insertions(+)
> 
> Index: linux-2.6/kernel/sched.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched.c	2008-02-28 20:05:27.000000000 +0530
> +++ linux-2.6/kernel/sched.c	2008-02-28 20:05:30.000000000 +0530
> @@ -8243,10 +8243,34 @@ static u64 cpuusage_read(struct cgroup *
>  	return totalcpuusage;
>  }
> 
> +static int cpuusage_write(struct cgroup *cgrp, struct cftype *cftype,
> +								u64 reset)
> +{
> +	struct cpuacct *ca = cgroup_ca(cgrp);
> +	int err = 0;
> +	int i;
> +
> +	if (reset) {
> +		err = -EINVAL;
> +		goto out;
> +	}
> +

Why not use

        if (reset)
                return -EINVAL;


> +	for_each_possible_cpu(i) {
> +		u64 *cpuusage = percpu_ptr(ca->cpuusage, i);
> +
> +		spin_lock_irq(&cpu_rq(i)->lock);
> +		*cpuusage = 0;
> +		spin_unlock_irq(&cpu_rq(i)->lock);
> +	}
> +out:
> +	return err;
> +}
> +
>  static struct cftype files[] = {
>  	{
>  		.name = "usage",
>  		.read_uint = cpuusage_read,
> +		.write_uint = cpuusage_write,
>  	},
>  };
> 
> 

Looks good

Acked-by: Balbir Singh <balbir@...ux.vnet.ibm.com>

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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