linux-kernel - Re: [RFC][PATCH v5 05/14] sched: add a packing level knob

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Date:	Tue, 12 Nov 2013 11:32:28 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, pjt@...gle.com,
	Morten.Rasmussen@....com, cmetcalf@...era.com, tony.luck@...el.com,
	alex.shi@...el.com, preeti@...ux.vnet.ibm.com,
	linaro-kernel@...ts.linaro.org, rjw@...k.pl,
	paulmck@...ux.vnet.ibm.com, corbet@....net, tglx@...utronix.de,
	len.brown@...el.com, arjan@...ux.intel.com,
	amit.kucheria@...aro.org, l.majewski@...sung.com
Subject: Re: [RFC][PATCH v5 05/14] sched: add a packing level knob

On Fri, Oct 18, 2013 at 01:52:18PM +0200, Vincent Guittot wrote:
> +int sched_proc_update_packing(struct ctl_table *table, int write,
> +		void __user *buffer, size_t *lenp,
> +		loff_t *ppos)
> +{
> +	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> +	if (ret || !write)
> +		return ret;
> +
> +	if (sysctl_sched_packing_level)
> +		sd_pack_threshold = (100 * 1024) / sysctl_sched_packing_level;
> +
> +	return 0;
> +}

> +#ifdef CONFIG_SCHED_PACKING_TASKS
> +static int min_sched_packing_level;
> +static int max_sched_packing_level = 100;
> +#endif /* CONFIG_SMP */

> +#ifdef CONFIG_SCHED_PACKING_TASKS
> +	{
> +		.procname	= "sched_packing_level",
> +		.data		= &sysctl_sched_packing_level,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= sched_proc_update_packing,
> +		.extra1		= &min_sched_packing_level,
> +		.extra2		= &max_sched_packing_level,
> +	},
> +#endif

Shouldn't min_sched_packing_level be 1? Userspace can now write 0 and
expect something; but then we don't update sd_pack_threshold so nothing
really changed.
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