Date: Mon, 8 May 2006 14:26:40 -0700
From: Andrew Morton <akpm@osdl.org>
To: balbir@in.ibm.com
Cc: linux-kernel@vger.kernel.org, lse-tech@lists.sourceforge.net,
       jlan@engr.sgi.com
Subject: Re: [Patch 3/8] cpu delay collection via schedstats
Message-Id: <20060508142640.675665c7.akpm@osdl.org>
In-Reply-To: <20060502061505.GN13962@in.ibm.com>
References: <20060502061505.GN13962@in.ibm.com>
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Balbir Singh <balbir@in.ibm.com> wrote:
>
> +/*
> + * Expects runqueue lock to be held for atomicity of update
> + */
> +static inline void rq_sched_info_arrive(struct runqueue *rq,
> +						unsigned long diff)
> +{
> +	if (rq) {
> +		rq->rq_sched_info.run_delay += diff;
> +		rq->rq_sched_info.pcnt++;
> +	}
> +}
> +
> +/*
> + * Expects runqueue lock to be held for atomicity of update
> + */
> +static inline void rq_sched_info_depart(struct runqueue *rq,
> +						unsigned long diff)
> +{
> +	if (rq)
> +		rq->rq_sched_info.cpu_time += diff;
> +}

The kernel has many different units of time - jiffies, cpu ticks, ns, us,
ms, etc.  So the reader of these functions doesn't have a clue what "diff"
is.

A good way to remove all doubt in all cases is to include the units in the
variable's name.  Something like delta_jiffies, perhaps.

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